Original subtitles

(CHOIR SINGING)

Who can remember what we learnt last lesson about chain reactions?

It's like dominoes, sir. That's right.

It's like dominoes.

When just one molecule is activated,

it can cause a reaction, which in turn releases...

unstable molecules.

They then trigger further reactions.

And so the chain gathers momentum.

See how it's branching and growing as it feeds itself.

L is the angular momentum quantum number. (MUTTERS)

L tells you the type and shape of...

Tells you the type of the orbitals.

L is the magnetic quantum number... Quantum number...

..tells you where the orbitals are along the X or Y...

Good luck, mate.

Home?

Home.

Today, we're gonna take a look at

the first chain reaction ever discovered.

Hydrogen and chlorine.

All you need to trigger this is UV light,

which you get by burning magnesium.

But, once the chain is in motion... it's unstoppable.

Chrome every time, sir.

James.

The er...flat's looking a bit tired.

So this is what you're doing with your day off.

Sprucing up the bachelor pad. I'm not sprucing.

'Marine Dream Blue'. Nice.

Look, haven't you got somewhere else to be?

I don't remember you booking the day off.

Community Partnership seminar, 3:00pm.

Enjoy.

(BIRDSONG)

I wasn't sure what you'd want to do.

The garage said they could fix it - Just get rid of it.

The interview isn't that bad, as long as you know your chemistry.

Make sure you do some mock interviews with Mr Drew,

if you do decide to apply. They asked me all the same stuff.

Glad to be of service. Anyone else?

Is it loads more work than A-level?

Well, it's a big step up, obviously.

But it's all right...most of the time.

Good. Well, I think we should give Adam a round of applause

to say thank you for coming back to talk to us.

That was good.

Erin had this bean plant.

She was supposed to grow it over the holidays

and measure it every day.

Mum carried on watering it for weeks afterwards,

and I just kept thinking, 'How is this thing still alive?'

'How is it possible that

this stupid little plant can keep on living and yet...'

We both realise how difficult this must be.

But do you feel able to let Richard respond?

Rachel...

I need you to know that your sister, and what I did,

will stay with me forever.

If I could do anything to change what happened...

All you had to do was think, 'I've had a nice boozy lunch.

Maybe I won't get in my car, this afternoon.'

How hard is that? I know I can't expect forgiveness...

but prison has strengthened my faith,

and as part of my recovery - YOUR recovery!

Of course. That's what this is about.

Rachel, please. Forget it.

Three years. Out in one. It's a joke.

You were right, OK?

I'm sorry.

I'm so sorry.

I know you don't want to hear it, but I think that was brave.

It was selfish.

Things will get easier, I promise.

With God's help.

LEWIS: Yeah, I'm not sure that I've got it right.

HATHAWAY: No, that sounds fine. As long as the juices run clear, you're OK.

Anything else?

Yeah, then leave it on a hot dish for 20 minutes to relax.

Thanks. Just as long as one of us is relaxed. (DOORBELL)

Ah...wish me luck.

Good luck.

(ENGINE STARTS AND REVS)

(CLATTERING)

Beautiful place this, isn't it?

What we got? - Deceased is a Professor Richard Seager, biochemist,

fellow of Benison College.

He was released from prison yesterday after serving a year for death by dangerous driving.

No signs of a break-in. Body was discovered by his wife, the Reverend Martha Seager,

crushed under his own car.

Bloody hell. I know.

You do read about these freak accidents, don't you?

No, sir, this is not an accident.

The car must have accelerated pretty hard

to churn up this much gravel.

I can't get to them properly,

but the first thing I'm seeing is multiple flaying injuries,

where the wheels have taken the skin away.

Suggests he was knocked down, then driven back over several times.

Yeah, all right, all right. I can see it wasn't an accident.

Just giving humanity the benefit of the doubt for once.

She left here the first time at around eight, if that's any use.

Sorry, who left at eight?

Rachel Cliff.

The girl who killed my husband.

Erin Cliff was the young girl involved in the fatal road accident with Professor Seager.

Rachel was Erin's sister.

And the Jag outside is the same car that killed Erin?

Yes.

It was my fault.

Rachel and her mother were on their own and I thought I could help.

What do you mean? I persuaded her to meet Richard.

I thought it would be good, but she left here angrier than ever.

She must have taken the keys from the hall...and come back.

Can you take us through what happened

in between Rachel leaving here

and you finding Richard's body this morning?

We had an early night. He was exhausted.

Then, this morning, when I took him his tea in bed, he wasn't there.

I thought he must be pottering in the garden...

..and then I found him.

How was your relationship with your husband?

Good.

We were happy.

But you didn't realise he wasn't in bed

until you took him his cup of tea.

So you weren't sleeping in the same room?

Well, prison makes things difficult.

He needed some time to adjust, so he slept in the spare room.

And where did you sleep last night? The main bedroom.

The one in the front, with the window open? That's right.

And you didn't hear anything?

No, not a thing.

Some people do sleep very deeply.

So deeply they miss a violent murder going on outside their window?

How's it looking, Laura?

Like a man under a car, at the moment.

I won't be able to judge lividity

till we get him out from under there,

but there's early rigor mortis in the neck and jaw.

So dead maybe five, six hours? There's something else, though.

Some small scratchings in the body work, with

what seems to be the same colour paint at the end of his keys.

It's a number.

500.

It looks like Seager wrote that, as he was dying.

Would that be possible?

Depending on his injuries, it might have been possible.

Why 500?

Look at all these search results for him.

He was quite famous, for a scientist.

What did he discover?

It seems to be more about his promotion of the idea of Intelligent Design,

that the complexity of the universe is due to an intelligent creator...

We know what it is, Sergeant. Sorry.

Anyway, Seager was a leading proponent.

He ran a lecture course, arguing that God and science aren't mutually exclusive.

I'm sorry I missed it.

Still, it explains why he was married to a vicar.

She claims she slept through the whole thing. You're not convinced?

Not for a minute.

How could anybody sleep through that kind of racket?

Well, if you find out, do let me know.

What's she mean by that? I think she's implying you're a snorer.

Val always said it was more of a snuffling.

Maybe she was being kind.

It's strange, you know?

After all these years.

Good strange? Yeah.

Really good strange.

So you should've ended up with something that looks like this,

with the intermolecular hydrogen bonding shown by the dashed lines.

Was everyone all right with that? Any problems at all?

Adam, do you want to hang on for 10 minutes at the end?

Right, let's move on to disulphide linkages and other covalent bonds.

There you go. Thank you. You're welcome. Rachel Cliff?

Yeah? DI Lewis, DS Hathaway, Oxfordshire Police.

Could we have a word?

What about? I'm her mother.

We understand you've had dealings with Professor Richard Seager.

'Dealings'? I've not heard it called that before.

He killed my daughter, if that's what you mean.

He was found murdered at home, this morning.

Oh, there you go. Maybe I'll buy a lottery ticket later.

Mum.

Under the circumstances, we do need to ask you some questions.

Ask away.

In particular, Rachel, we need to speak to you about your contact with the professor last night.

I'm sorry.

You promised me.

You promised me you wouldn't go around there.

Adam said he wouldn't let you go. Martha thought it might help.

Oh, well, if Martha thought...

Rachel, is there somewhere we can talk in private?

You'd think it'd be enough, them taking my little girl.

But then they had to try and take Rachel too -

phone calls and letters,

and 'come to our church', 'come to our house'...

And now... Now we've got the police round here, asking questions.

If you and your daughter would be willing

to give us DNA samples and prints down at the station...

Fine. Whatever.

Thanks.

It would also be helpful to know where you were

in the small hours, this morning?

I was reading Heat magazine in the waiting room of A&E.

I managed to twist this when I was putting the bins out.

(PHONE RINGS) Excuse me.

Lyn? Everything OK?

When was this?

It was weird. It was like, she was his wife, so I hated her.

But it also felt like she understood.

Like I could say things to her that I couldn't say to my mum.

So tell me about last night.

I finally realised it was all an act.

She was just pretending to be nice so I'd forgive her husband.

She said that you were really upset when you left.

Where did you go after? Went back to my boyfriend's. Got trashed.

Where were you during the night?

Still in my boyfriend's room in town.

Adam Tibitt. He's a first year at Benison College.

We went to school together.

Can anyone else confirm that you were there all night?

Why? What's she been saying?

We just need to establish your whereabouts.

She thinks I killed him, doesn't she?

Well, you know what? I wish I had.

Hang on a minute.

Everything all right?

I... I just need a word.

Sounds ominous. That's the sort of thing you say to your suspects.

Yeah, well, I don't usually offer these to my suspects. Come on.

My old granny used to pay me in giant chocolate biscuits for mowing her lawn.

Sounds like an excellent trade-off. It wasn't bad.

I stayed with her almost every year.

Little bungalow out at Whitley Bay.

Do you know when I last saw my grandson?

Christmas. For a day-and-a-half.

Took him a toy fire engine that he already had.

Take a week off. Go up there.

Apparently he's been in hospital the last three days.

Lyn just phoned me a couple of minutes ago.

Is he all right? Well, not in hospital.

Back home, running riot, according to his mam.

The thing is she didn't even call me until the whole thing was sorted.

Didn't want to worry me.

I don't even feel part of my own family any more.

Anyway, that's it now.

I've been going on about retiring for ages. Time I chucked it in.

Put my family first...

..and Laura, if she'll let me.

I'm sure she will.

Thing is, when I go, there'll be a DI job come vacant.

You should apply for it.

Set up a meeting with Innocent, let her know you're interested.

Yeah, thanks. I don't think I'm... Oh, come on.

You're more than ready. No, I don't mean that.

It just wouldn't feel right, if you went, for me to stay.

Well, I hate to break it to you, but you're too young to retire with me.

Much as I'd like us to have an allotment and a nice little sailing dinghy together.

Well, I've heard worse plans.

(CHUCKLES)

Seriously, though, you're ready to go and do this on your own - so go and do it.

I'll think about it. Think about it?

Mm-hm.

Well, why don't you think about it on your way down to the prison?

Find out if Seager had made any enemies while he was inside.

I'll see what I can dig up at his college.

I'm sorry, but the exams are two weeks away

and you're still struggling with basic concepts.

But I'm working as hard as I can. I mean I...

Why don't we see how these exams go and then talk again, OK?

But it might be that you're better suited to another course...

..at another university.

Thanks.

(TOOLS WHIRRING) Start the application straightaway.

Doctor Yardley? Detective Inspector Lewis.

I need to speak to you about Professor Seager.

Yes?

I'm afraid I have some bad news. He's dead. I know.

What do you want from me?

Well, I'm told you're the Master here,

and I was hoping you could give me some information about his academic life,

if it's not too much trouble.

Oh, no, not at all. Forgive me, I'm a bit...

Do you know anything about 17th-century roofs?

Not my specialist subject, to be honest.

Nor mine. Turns out they're expensive.

Apparently ours is on the verge of collapse.

I'm sorry to hear that.

Well, how can I help?

Did Professor Seager have any enemies that you were aware of?

The usual intellectual squabbles,

but nothing serious that I can recall.

And what was the plan for after his release?

Was he coming back to work? Well, that was a difficult one.

Richard had a brilliant scientific mind. Truly brilliant.

But with fellowship comes moral responsibilities.

We held a ballot, and the majority vote was to revoke his fellowship

and promote Stella to his Chair of the Chemistry role.

Stella? Doctor Stella Drew, Richard's protegee.

I think she's the best person you can speak to.

Knew him much better than I did.

Any idea where I might find her?

You could try her rooms. Old Quad, top of J Staircase.

Doctor Drew?

DI Lewis, Oxfordshire Police.

Hello. Stella's at work.

Is this about Richard? Yes.

Martha phoned us this morning. Sorry. You are...?

Carl Drew. I'm Stella's husband.

That's the last time I let my Year Nines loose with the iodine.

Please come in.

So you knew Professor Seager?

He taught me and Stella when we were undergrads here.

Stella decided to stay on and I was kind of stuck with him.

Not his biggest fan, then? Oh, he wasn't that bad.

Just a little bit, you know... Oxford.

If you weren't ridiculously gifted like Stell,

you basically were invisible to him.

How well did you know his wife? Far too well.

She's Stella's best friend. One of mine, too.

We've been treated to the ongoing saga of their marriage for years.

The saga? It's been dragging on forever.

Richard filed for divorce a couple of years ago,

Martha was fighting it and he never quite moved out.

I think she was almost glad when he was sent to prison.

At least it meant he wouldn't leave her.

Stella knows more about it.

Greenaway Labs, science park.

She'll be there till late.

James? See what you can find out

about a Doctor Stella Drew of Benison College,

then meet me in the science park in about an hour.

Can we make it more like three? I've got a bit sidetracked.

Oh? What by? Stapleton did some digging,

came up with years of debate in the scientific press

between Seager and the Master of Benison College - Graham Yardley.

I just met him. A bit cagey.

Well, he's waged war on Seager since the '80s,

arguing that his Christian teaching should be banned from universities.

Really. I don't think he got around to telling me that.

How's that thinking going?

Have you fixed up a meeting with Innocent yet?

No. But I managed to get in touch with Seager's prison officer.

Changing the subject. OK.

Apparently Martha forgot to tell us that he was a raging alcoholic

and had been for a decade.

He had a drink problem? Are they sure about that?

Everyone in the prison says the same.

He spent his days praying, going to alcohol recovery meetings

and talking about how to lead a better life when he got out.

Visitors? Only Martha the entire year -

with the exception of one visit 10 days ago from Adam Tibitt.

Rachel's boyfriend. Interesting.

Now, where are we?

Greenaway Labs... I realised after you called,

I've come across Stella Drew before.

I heard her interviewed on Woman's Hour a few months ago.

Woman's Hour? It's an excellent programme.

You should download the podcast.

And what did she have to say for herself...on Woman's Hour?

She was quite impressive, actually.

She made a breakthrough in Alzheimer's research

while she was a post-grad, became a Fellow in her early 20s,

campaigns for more women in science...

Oh, God. One of them. What, feminist?

No. Over-achiever.

They make me uneasy.

He was my mentor for 15 years.

Everything we're doing here's down to him.

It's research into dementia - is that right?

Into Alzheimer's, yes.

My particular research stems from my doctoral work on the Amyloid Hypothesis.

Whether amyloid fibril formation is a cause of neurodegeneration

or if another protein such as...

I lost you at 'hypothesis', didn't I? You might have.

Never mind.

So let's get to the point. Carl called.

He thinks he put his foot in it about Richard divorcing Martha,

and now you want to know whether or not my friend killed her husband.

We wouldn't have put it quite like that.

Presumably it's one of your hypotheses?

I can tell you that she isn't capable of it.

I've asked her to stay with us until she's ready to go back home.

I wouldn't have done that if I thought she was a risk to anyone.

Surely you should be speaking to

the family of the little girl from the accident?

We have to keep an open mind for the moment.

You run Professor Seager's research team now. Is that right? Yes.

And you were promoted to his Chair of Chemistry.

And you think I stood to gain from his death?

Just establishing the facts.

No, that's fair enough.

The facts are that I have taken over his positions,

but that happened while he was in prison.

When there was controversy about if he should be allowed to stay on at the college,

I voted in his favour.

Any way we can confirm that?

The Master's secretary should be able to show you the ballots.

It wasn't anonymous. Fine, thank you.

Does the number 500 mean anything to you?

A measurement? A reference to a chemical?

500?

No, not particularly. Why?

Just part of our investigation.

Could you keep it in mind? Let us know if anything occurs to you?

Course.

Surely if Seager wanted to point to somebody in the chemistry department

he'd have written their name, not their extension number.

There could be a connection. If all the phones begin with extension 500

there might be a voicemail on one of them.

I could ask the university to grant me access.

Are you proposing phone hacking, Sergeant?

It's not phone hacking if you ask nicely.

From the degree of hypostasis and the decreased fluid pressure behind the eyes,

I'd put time of death at 2:00 or 3:00am.

What? Nothing. Sorry, carry on.

The contusions, multiple fractures

and tyre impression are all consistent with...

I'm sorry. I'm not smiling at... Oh, God, sorry.

It's all a bit odd now, isn't it? You and me and...

Well, I don't know. Some of our best times together have involved a mangled corpse.

Yeah, that's just my point. It's not normal, surely?

We do have to work together, Robbie.

I hope this isn't going to be a problem.

Well, I have been having a think.

You know I'm always banging on about retiring?

What would you say if I just did it?

I'd say about bloody time.

Would you?

Really, I mean, you'd be all right about being with a pensioner?

Would that pensioner have my dinner on the table when I get home

and rub my back for me till I can retire too?

I'm sure he would.

Then I'd love it. (DOOR OPENS)

(ORGAN MUSIC)

Reverend?

Martha!

Hello?

Oh. Could we have a chat?

Is there any news?

Why are you lying to us?

I'm not sure I know what you mean.

Why didn't you tell us that your husband was an alcoholic?

Because he was in recovery.

And that he'd asked you for a divorce?

I didn't say anything because it was all in the past.

Richard filed the petition before he went to prison,

but only because he wanted to protect me from his drinking.

He did it because he loved me.

Had he withdrawn the divorce petition?

No. But he would have done. I'm certain.

If there's anything else you haven't told us, Martha,

we really do need to know.

There's nothing.

It must have been difficult to stick by him through the alcoholism,

through the accident, through prison.

And at the end of all that, to find that he's still filing for divorce.

What are you saying?

Did he reject you?

Did you snap?

I went to his room and tried to comfort him.

He pushed me away.

He always said he was leaving because of the drink -

no other reason.

So, when he was released, and he was doing so well,

I thought I was getting my husband back...

..but then, last night, he told me I wasn't.

He said the drinking wasn't just about work - it was about me.

I went upstairs and I lay in our bed,

on my own, until I went to sleep.

I didn't hurt him.

I didn't expect to be saying this, but I think I believe her.

You're just a sucker for a dog collar. It's true.

But if she did snap, why would she use the car? It's a bit elaborate.

Well, maybe she was driving away and he was trying to stop her?

Look, I need to check on how they're getting on down at the station.

Why don't you try and track down this Adam Tibitt?

See if he admits to visiting Seager in the prison.

(DRINK BEING STIRRED)

Cheers.

Good little artist, wasn't she? Erin? Yeah, she was brilliant.

I gave her a paint set for her eighth birthday,

and then the pictures just kept on coming.

So, tell me what you can about Professor Seager.

Did you know him before the accident?

Well, I met him once, for my interview...

..and the strange thing was - I actually liked him at the time.

Did you see him again after? Not at college, no, no, no.

He was in prison by the time I came up.

But then...then he started writing these letters to Rachel

and it was getting creepy -

every week, wanting to meet up when he got out of prison.

So I went to see him, asked him to leave her alone.

And what did he say? Oh, he promised he'd stop.

But by this point it was too late.

Martha had already gotten into her head

and persuaded her it was a good idea.

So did you go with Rachel when she went to see Seager last night?

Yeah, I waited outside.

What did you do after?

We came back here.

Hasn't Rachel told you this? I need to confirm it with you.

Where were you between the hours of 2:00 and 3:00am?

Why are you asking me that?

I'm not accusing you of anything.

Well, I was asleep, right there. With Rachel.

Look, I've got my exams in less than two weeks,

and I'm really behind with my revision so...

Mm. Good luck with that.

I'll... I'll try not to disturb you again.

(WHISPERED PRAYER)

(SIZZLING)

Robbie?

What's this from HR about your pension forecast?

Ah, I was going to talk to you about that, once I was certain.

You're going?

Well, I'm giving it some serious thought.

Has something happened I should know about?

Old age.

It happened when I wasn't looking.

Well, probably when I was sitting here,

trying to figure out stuff like this.

Oh, don't be so bloody maudlin. You love it really.

No, I love my kids.

I love my grandson.

I quite like Laura.

But it'd be nice to spend some time with them.

Then I'm glad you're thinking about it.

That's not the same as believing you'll go through with it.

It's reassuring to know that one of us looks forward to going home at night.

So how's the current puzzle looking?

Well, house to house didn't come up with anything,

and...Seager's place is too remote for CCTV to be much use.

Well, maybe Hathaway's solved it and you can get off early?

Alas not, Ma'am, but the phone company got back to me.

Seager took a 30-second call from a pay-as-you-go mobile

at 2:20 this morning.

They can't trace the pay-as-you-go,

but they say it was only used to make that one call.

So the killer called Seager to lure him onto the driveway.

And it was someone he'd agree to see in the middle of the night.

An affair? That's what I was thinking.

Then there's this. Screen shot from the John Radcliffe.

It shows that Debbie was in A&E all night.

Well, that's good. Just as useful to know who it isn't.

What about this '500' - the thing he scratched into the paintwork?

Eight phones in the lab. All have extensions beginning 500.

None of the messages left seemed significant.

Nothing more concrete? Not yet.

I've got two teams going through his papers,

his computers, but so far nothing.

There must be something else.

Come on, Cambridge - your starter for 10.

Find out what it means.

Do you fancy a pint?

Yeah. Well, usually.

It's just Laura's... No, don't worry about it.

We'll do it another night.

You know what, though? Ma'am?

James wants a word, if you've got a minute?

(KNOCKING)

(HE SOBS)

(TV IN BACKGROUND)

Early start. Someone's trying to impress.

Yeah, thanks for that, last night.

How'd it go? It didn't.

If it's all right with you, I'll decide when I go for promotion,

if I go for promotion.

OK. Message understood.

I got the results of the Fellows' ballot.

Stella was telling the truth. She did vote for Seager to stay on.

Oh, right. So she wasn't after his job.

But the weird thing is, Yardley also voted the same way.

If he objected to Seager's beliefs that much,

you'd think he'd get rid of him.

Robbie? Hello.

Did I forget something? No, but the lab have just called.

They've got DNA results from the car. Anything helpful?

There are dozens of DNA profiles in there -

his wife, his colleagues, and some that we can't identify.

One hair on the driver's headrest had some follicle matter attached,

and the DNA from that follicle is an exact match for Rachel Cliff.

Morning.

Two full English.

Your pancakes are on their way. Promise.

We were hoping for another chat with Rachel, if she's around.

Does it look like she's around?

Any idea where we might find her? It's quite urgent.

She's 18. I don't keep tabs on her.

Shall we try her boyfriend? Try wherever you like.

She's not going to say anything she hasn't already said.

OK. Thank you.

(WORKMEN LAUGHING)

Whoa.

This is important.

Are you sure you've never been inside Professor Seager's car?

No, I told you. Why would I want to go anywhere near that thing?

In that case, we'd like you to come to the station with us

and answer some questions on the tape. What?

Are you arresting her? You can't! You can't arrest her!

Not arresting - no.

But we do need your help with our investigation.

I haven't done anything.

And it would be better for everybody if you'd do that voluntarily.

(KNOCKING)

Are the police in there? There's no problem.

They needed to check something.

Sorry to interrupt, but the Master's asking if you can pop down to the main quad.

Thanks. Tell him we'll be there in a few minutes.

He says it's urgent.

Don't go anywhere.

Call her, now.

It would appear we have a...situation with our roof.

What kind of situation? I think it's best you take a look,

but your discretion would be appreciated. It's delicate.

This gentleman will show you.

This way, gents, if you would.

(CHOIR SINGING)

♪ THOMAS TALLIS: If Ye Love Me

♪ Keep my commandments

♪ And I will pray

♪ The Father...

It's up here, then.

(CLANKING)

(FOOTSTEPS OVERHEAD)

Just through here.

Mind your step.

(CHOIR IN BACKGROUND)

Good God.

How long has this been up here?

Sir? Hm?

Maybe it wasn't a number that Seager was scratching into his car.

It was a name.

Time of death, Doctor?

You need a forensic anthropologist on this one.

All I can say for certain is it's an adult female, multiple fractures, including the skull.

So a fall? Beating with a blunt object, maybe?

Any idea at all how long she's been up here?

A decade or more?

Really not my area, I'm afraid. Prefer a bit more flesh on my bones.

What?

Office ran a check.

There's a record of a Soo-Min Chong who disappeared in June 1998, aged 20.

She was an exchange student from South Korea, studying chemistry at Benison College.

So she'd have been taught by Professor Seager?

Finished a year assisting his research group.

Booked a flight home, never turned up. Must be her.

Wouldn't have been easy - dragging her up that lot.

Do we assume she was killed here? I don't think we can assume anything.

I can't imagine you could move a body

through the college without somebody seeing.

Laura reckons it was a fall or a beating.

What?

Snapped clean off.

Right, where were we?

Tell us again where you were in the early hours of Tuesday morning.

In my boyfriend's room in Benison College all night.

And have you ever been in Professor Seager's car?

No.

If you're not going to arrest me, why keep asking me the same questions?

You're free to leave at any time.

But I'd like you to stay and help.

In particular, I'd like you to explain

how a hair found on the driver's headrest of the car that killed Professor Seager

is a perfect match for your DNA.

It must be her. Martha must've put it there.

The only reason we're able to get this DNA from the hair at all

is because it still had the follicle attached.

Are you saying that Reverend Seager's been pulling your hair out?

No. I don't know.

It's not her, is it?

Isn't it?

She's 18.

She'd have been in nursery school when Soo-Min was killed.

We can't assume a connection.

Professor Seager's death might have nothing to do with our skeleton in the attic.

Well, he spent his dying moments writing 'Soo',

and then the body of a girl called Soo-Min turns up two days later?

Well, if you're so sure there's a link,

it makes sense for you to handle both investigations.

Soo-Min's missing person's report - enjoy.

It's all a bit convenient, though, isn't it?

The hair in the car just happening to give us a nice DNA match?

Of course, another alternative is that Rachel's hair ended up

in the car because it came off someone else.

Adam, please? Look, Adam, we can sort this out.

Adam, please!

According to the original investigation,

Professor Seager was the last person to see Soo-Min before she disappeared.

Give us a look.

In his statement, he said she came to his office in college

on the 17th June to get her exchange credits signed off.

She stayed for 20 minutes and then left. The last she was seen alive.

Perhaps she never left his office.

What's this? Statements from study mates and friends

saying that she was quiet, super-clever, musical.

She was Martha's organ scholar in chapel, apparently.

And a statement from her ex-boyfriend - Carl Drew.

No running.

Soo?

We'll need the forensics to be sure, but we think it's her.

We understand that you were close?

I'm not sure about close, but we were a...

Oh, God.

Excuse me.

Yep?

Good.

When I started my doctorate here, there was a thing between the graduates -

a sort of tradition - to see who could bed the most undergrads.

You know what it's like.

So, I went for Soo. This was way before Stella and I got together.

But she was Soo's lab supervisor and I was trying to get her attention.

By having sex with her research assistant?

It wasn't my finest hour.

But it was 15 years ago.

So what happened?

It wasn't serious.

And we said goodbye a few days before she was due to go home,

and that was the last time I saw her.

Remind me where you were the night the professor was killed?

In bed with my wife.

I'm sorry, but what has the fact that I went out

with Soo-Min 15 years ago got to do with Seager?

Probably nothing.

As I say, just building a picture.

They're saying they're going to be in there for another 24 hours.

He'd hate strangers going through his things.

You do know you're welcome to stay with us for as long as you need to?

I know. You and Carl have been so kind.

But I feel I want my own...

Adam! What's wrong with you?

Oh, God!

It never ceases to amaze me how much a woman can get into one suitcase.

You owe me a drink.

In fact, several drinks.

Number one. Dental records from the other side of the world,

confirming this is indeed Soo-Min Chong

from the Itaewon district of Seoul.

Number two.

The initial report I was able

to drag out of the forensic anthropologist.

He believes the skeleton dates back to the late '90s

and that he finds me "unnecessarily pushy".

Yeah, Laura, I have - And number three...

A luminol test showed a tiny stain on the suitcase was dried blood.

The DNA was pretty degraded,

but there was enough for a reasonable comparison

and it's a match for Professor Seager.

Seager's blood is on Soo-Min's suitcase?

Here - under the handle.

I knew there had to be a connection.

Where's Hathaway?

We should ask the Reverend Martha

if she can shed any light

on what was going on between Soo-Min and her husband.

How much longer are you people going to be?

Every hour you spend pulling our chapel apart

is costing this college a fortune.

There's the skeleton of a murdered girl in your attic.

It'll take as long as it takes, I'm afraid.

She's identified as a student here in the late '90s - Soo-Min Chong.

Hundreds of students pass through this college every year.

I can't be expected to remember them all.

Not even the ones that mysteriously vanish?

There can't be too many of those, surely?

Are you all right, Adam? No!

You've got to stop harassing Rachel. She... She can't take it.

This'll take time... We're not harassing her.

You're trying to frighten her, saying her hair was in the car. It can't be.

She's never been near it. How can you be sure?

She's not a liar. She was with me all night.

Asleep. How can you be certain she was with you all night?

I just am.

I'm worried there's something you're not telling me.

Well, there isn't. If your theory's right,

and Rachel's never been near that car,

we have to ask ourselves how her hair got onto the driver's seat.

One answer to that question is that it came in on your clothes cos you were the driver.

You don't know what it's like. What what's like?

Not being good enough. Being surrounded by people who are.

People who get it.

I'm not meant to be here... I don't want sob stories.

I want to know what happened that night!

I know Rachel didn't leave my room because we didn't go to sleep.

She stayed up with me all night because I couldn't stop crying, OK?

I'm pathetic. Anyone confirm this?

That I'm pathetic? Yeah, sure. Try my tutors, my parents, my lab -

That you both remained in the room all night.

Forget it.

You said you'd come straight home. Where have you been?

Nowhere. I went for a walk.

Leave that. It's Adam.

It's always Adam! You can phone him back.

Look, tell me what they said. They're having a go.

Seeing if I'll freak out. Mum...

I'm telling you it's fine, OK?

She was the organ scholar during my second year as chaplain here.

Sweet little thing.

I don't think Richard ever mentioned her, though.

Not at all?

I'm not sure I even knew she was a chemist.

Your husband said you supervised Soo-Min's lab work for a while.

Was that part of Professor Seager's Alzheimer's research? Yes.

She worked for a few of us in the group.

Vaguely competently, as I remember.

That good? Well, she wasn't exceptional.

But according to the missing person's report,

she seems to have been extremely clever.

Well, it's Oxford, Inspector. Everyone's extremely clever.

And there's no way your opinion could be tainted

by the fact that she was sleeping with Carl?

Of course not. We weren't together.

Apologies for having to ask you this, Reverend,

but is there any possibility that your husband was having an affair

during Soo-Min's time in Oxford?

That's absurd. Look, I'm sorry,

but you said this girl had been dead for years.

My husband was murdered two days ago.

Why aren't you doing anything about that?

We are. I promise.

We believe he might have tried to communicate her name as he died.

What do you mean "communicate"?

I can't say any more at the moment.

Do you have any idea why he might have wanted people

to make a connection between himself and Soo-Min?

He wouldn't.

He hardly knew her.

She was so important to him he used his dying breath to write her name,

yet never even mentioned her at home.

Sounds like an affair if you ask me.

You lost something?

Yeah, my phone. Must have left it at the school.

What was it Stella and Seager were researching again?

Alzheimer...

You're funny.

L is the angular momentum quantum number.

L tells you the type and shape of the orbitals.

Help! Help!

I'd say it's been less than an hour.

Nothing obviously suspicious.

No indications of a struggle

and the marks on his arm suggest a history of self-harm.

No sign of a suicide note on him? No.

But the words on the board and the study notes at full volume

send a pretty clear message, don't they?

Is he OK?

He found him. Cut him down.

Oh, God. I know.

The headmaster called. It's Adam?

We had a tutorial yesterday.

I basically told him he was failing.

It's not your fault. I didn't offer him any help.

Adam was your pupil before he went up to uni, is that right?

I was his chemistry teacher. He was a good lad.

Did you see him this afternoon?

No. I went home ten minutes after we finished talking.

There was some writing on the board in your class. 'Thanks, Sir.'

Was that there when you left?

No.

You mean he's blaming me?

It's not clear yet.

But can you imagine why he would choose to do this in your lab?

He must've been angry at me for pushing him to apply.

I thought it's what he wanted. I really thought he'd do well.

Mr Drew? A word, please? Sorry, the Head. Do you mind?

Course not.

How are you doing?

Fine. You told me to expect it in this job.

You were right.

I can never get my head around kids killing themselves over exam stress.

We should sound out Rachel.

Maybe she confessed to him after our interview,

and that's what triggered it.

Cos otherwise, why today?

What happened today that tipped him over the edge?

Sir?

I'm concerned that I put undue pressure on Adam

when I spoke to him in college earlier.

What kind of undue pressure?

He was so insistent that the hair couldn't have come off Rachel,

there was just something strange about the way he seemed so...

So I suggested that it transferred

from his clothes cos he was the one driving the car.

Well, that's not undue pressure.

That's a sensible line of inquiry. Come on.

Hold on. Modern miracle? Where's the crutch gone?

CCTV shows her in A&E the night of Seager's murder.

You wouldn't hang around in there all night unless you had to.

I might. If I knew somebody was going to be killed

and I fancied a watertight alibi.

I've no idea where she is. She ran out the door, she was a mess.

Yeah, I'm sorry. They shouldn't have told her about Adam over the phone.

We said we'd come round. Yeah, hours later.

Do you know when Rachel last had contact with Adam?

We need to piece together what happened.

For his family, if nothing else.

They spoke on the phone at five, five-thirty, maybe.

Any idea what they talked about?

Do you tell your mother what you talk to your girlfriend about?

You'll have to ask Rachel - if you can find her.

How's the ankle?

Fine. Better. Thanks.

Only it must have been pretty serious -

six hours in A&E and it healed overnight?

What are you now, a copper or a doctor?

I only asked the question. Oh, you lot with your questions!

You ask all the questions,

but you don't actually listen to the answers, do you?

I'll tell you one thing they did talk about. They talked about you.

Adam told Rachel what you'd said to him -

she couldn't get him to calm down.

A boy under that kind of pressure

and a girl still grieving for her sister.

But it's OK, isn't it, because you've got a badge.

She's just lashing out because she wants to avoid talking

about her alibi because it's clearly dodgy.

You can't take it personally.

She's right, we don't listen. All we do is interrogate.

Yeah, well, that's the job.

We ask people difficult questions.

It doesn't mean we're responsible for their decisions.

Oh, I don't know. Well, I do.

Look, take some time off tonight.

Come and have dinner with me and Laura. No, thanks, I'm all right.

You wouldn't be interrupting - it's a takeaway. Really. I've got... plans.

Thank you, though.

Interesting. Taste those.

Mm, yes.

I don't care about the reference number.

I just want you to go out there and start looking or making...

Mrs Cliff?

Oh, God.

It's Rachel.

She's not answering her phone and her friends haven't seen her.

I didn't know what else to do.

Is this a craft project or a cry for help?

It's the only way I can get my head around how these two are connected.

I still think you're gonna miss this

when you're growing carrots and watching Countdown.

I'll find plenty to keep me busy. Like what, though?

What are you actually going to do? What does anyone do? I'll potter.

Sir, I've just seen Debbie Cliff at the front desk.

Rachel didn't come home last night.

That's all we need. Is there a report out for her?

Desk sergeant's working on it. Hobson wants to talk to you.

She's got the lab to cross-check Adam's DNA

with the unknown DNA profiles from the car,

and we've found a familial match on one of them.

Familial match?

My wife's in a bit of a bad way. I'd rather let her sleep if that's OK?

That's fine.

I'm sorry to bother you at a time like this.

No, no, you're just doing your job.

I don't know what I can tell you, though.

We don't understand it ourselves.

Did Adam ever talk to you about what was troubling him?

I...I think it was all just building up.

Exams, worrying about his girlfriend,

and then that man coming out of prison.

Professor Seager. Did you ever meet him?

No. I've heard what happened to him though.

Have you ever been in his car?

No. No, of course not. Why do you ask that?

We've found DNA belonging to one of Adam's close relatives in there.

Either a parent or a sibling.

Well, that can't be right.

He doesn't have any brothers or sisters?

He was our only child.

In that case, I'm afraid we will need a word with your wife.

No, look, please let's... let's not involve Liz.

I...

I did meet him.

And I... I have been in his car.

It feels like we're throwing you out.

Are you sure this is what you want? Honestly.

I just need a proper night's sleep in my own bed.

OK.

You'll give us a shout if you need anything, won't you?

I will. I promise.

His teacher told us about this... this course

where you could have... proper coaching.

Carl Drew's course?

Yeah. Yeah, that's the one.

Mr Drew mentioned this college

that he knew of where sometimes, for the right student,

it might be possible to... stack things in their favour.

Are you saying you paid to get your son into Benison College?

A 200 grand donation to the roof fund

in exchange for an easy interview and a place.

We... we did the deal in Professor Seager's car.

Who else was involved? It was just those two.

And, oh, the Master, Doctor Yardley.

Adam had no idea until yesterday.

He found out? Well, Seager promised he would never know.

Then this letter turned up from the prison a couple of months ago

saying that he'd changed his tune.

Suddenly it was all morally wrong.

He was giving me ten weeks to talk to Adam myself before he blew the whistle.

Do you still have this letter? Adam made me show it to him.

It was only then that he told me that the man was dead.

So I could have got away with never telling him at all.

Our last conversation didn't... have to be me humiliating my son.

It could have been me telling him that...

..that I love every bone of him

if he never passed a single exam in his entire life.

Sorry.

I'll get that letter.

I'm sorry, what did you say your name was again?

DS Hatha... Erm... James.

You're the one who found him. They said that you tried to help.

I didn't help him. But you tried.

Thank you. Thank you, James.

DI Lewis, please.

OK. No, no. No message.

Well, I guess it's all there, isn't it?

I just wanted something that was mine, you know?

I got fed up of being the other half of the great biochemist.

So you set up Oxbridge Edge? It's a legitimate coaching business.

There were only a handful of occasions when it turned into anything more.

And how did those occasions work?

Sometimes, with particular families,

you could tell they would do anything.

I'd scope them out, and if they were receptive,

I'd put them in touch with Seager.

It was a huge risk, obviously.

The University would have come down on us like a ton of bricks.

But if we could convince Yardley

that it was watertight, he'd give us ten per cent.

Did you receive one of these letters from Seager?

A couple of months ago. And what would that have done to you?

Look, I see where you're going with this, but I didn't kill him.

Hi. That was pretty horrible.

I don't know why she wanted to go back there so soon when it's...

Is everything OK? Carl?

Well, the college needed money. That was a way to get it.

I think it's the only thing

that Professor Seager and I ever saw eye to eye on in 30 years.

But you didn't see eye to eye anymore.

Seager was going to confess, you knew that.

He was going to end your career.

I took on this Mastership with a very public promise

to turn Benison's fortunes around.

I staked my reputation on it.

But I've failed.

We reached the point of financial no-return six months ago.

The college will be forced to merge, leaving its Master without a future.

So there's really nothing

that Richard's spiritual cleansing could have done

to make things any worse.

It's me. Call me as soon as you get this.

I need to see you.

Carl Drew, Yardley and Mr Tibitt, Adam's dad.

Plus any other parents who received the same letter.

Any one of them could have killed Seager to stop him talking.

True. But... how does that connect to Soo-Min?

Maybe it doesn't. You don't believe that.

Anyway, what about his blood on her suitcase?

So he was her tutor, he carried her suitcase once. It doesn't prove he killed her.

Or that Seager was killed because of Soo-Min.

Maybe we started in the wrong place, starting with Seager.

The answer has to be with Soo-Min.

Come on. Where are we going?

Back to the station, where we've got an entire suitcase full of evidence.

You didn't have any plans for tonight, did you?

What exactly is it we're looking for? No idea.

But we're going to look at every photo, every book,

every page of every folder until we find it.

Oh, my God!

Uniform have started a door-to-door. It's definitely her.

First Seager, now his wife.

She hasn't been in there long - a couple of hours.

Drowned?

No, there's a puncture wound on the chest, so stabbed then dumped most likely.

Given the location of the wound, there would've been a lot of blood at the scene.

Martha's house is just upstream from here, isn't it?

Let's head over there.

Did you get anything? Not yet. Someone's done a good job.

But one of the boys noticed this.

The missing one doesn't seem to be here.

Ah, that's not good news.

I'm not sure I follow.

Well, Seager's murder seemed to be carefully planned -

the pay-as-you-go phone, car keys stolen in advance.

But if that's the murder weapon,

then whoever stabbed his wife didn't even think to bring his own knife.

And if it's the same person, they're getting desperate.

According to the calendar in there,

she kept a regular appointment with her GP.

The next one was today at three so I thought I might go.

Yeah, why not? See what you can find out.

Can you keep us up to date with the door-to-doors?

Just one thing so far, sir -

a neighbour said she saw someone turn into the driveway last night.

She recognised him because he used to teach her daughter. A Mr Drew?

What time was this? Around six.

Right. Thanks.

No need to let on that we can place him at the scene.

You go and keep the GP appointment.

I'll go and see what his wife might give away.

I should never have left her in the house on her own.

Where did you go after you dropped her off?

I went straight home.

I saw you.

I discovered my husband was a fraud and then I was here until late.

How late? 2am... maybe?

That's what I do when things are bad. I work.

So you wouldn't be able to account for Carl's movements last night?

No.

But why are you so worried about where Carl was?

You can't seriously think he had anything to do with this?

If you look at the photo the manufacturer sent over,

you'll see the pattern at the hilt of the knife

matches the bruise pattern left around the wound.

Hang on.

James? I've just been speaking to Martha's GP.

We've been asking the wrong question.

Instead of asking ourselves why Martha was able

to sleep through her husband being murdered outside her window,

we should be asking how the killer knew that she'd sleep through it.

OK.

Her doctor says she kept pestering him

to increase her prescription of sleeping pills,

but he said no because he thought she was getting dependent.

Then all of a sudden, one day, the pestering stopped,

and he says he suspects she was getting the supplies from elsewhere.

Another person supplying her? Well, exactly.

If her killer was feeding her addiction, then he was helping her drug herself.

Maybe Martha figured this out and confronted her supplier.

Right. You need to find the pills.

If we can prove that Carl's the one

that supplied Martha, I reckon we've got him.

Dark matter. That is a very good example

of one of the big scientific mysteries.

Oh, we're nearly finished here.

Do you need me to...? No, no, no, carry on. I can wait five minutes.

Right.

We'll make this the last one.

Some of our scientists believe

that over three-quarters of the matter in the universe is invisible

even to the most powerful telescope.

They call this substance dark matter.

If this theory is right,

then the answers to some of our most important questions

about the universe might lie not in the things we can see...

but in the things we can't.

Stella knows already?

Why didn't she call me?

Can you tell me what you did yesterday after I spoke to you?

I listened to my wife shout at me for an hour.

Then she stopped shouting... and wouldn't talk to me.

Eventually I went to see Martha.

So you admit that you were at the Reverend Seager's house yesterday evening?

There is nothing to admit.

I...went to see if she'd talk some sense into Stell.

But there was no answer.

I know you're not a fan of the blindingly obvious, but I'll state it anyway.

The first 24 hours following a murder are too precious to waste on a 15-year-old case.

Dark matter.

What?

It's not what we can see that's important, it's what we can't.

Look at this, look at this.

Soo-Min's lab notes -

they're all meticulously catalogued by project and supervisor.

Professor Gilchrist, Dr Easom, Dr Marbler...

But when we get to Professor Seager's section - nothing.

Why there's no record of the work she did for him?

If she was that well organised,

she'd have had it all backed up on one of these.

According to the inventory from Digital,

you're looking for a section called "Amyloid".

There should be a Professor Seager file in there.

"The Amyloid Hypothesis. Fibril Formation and Neuro-degeneration."

Amyloid hypothesis. Don't pretend you know what it is.

I'm sure I've heard of it.

I think it's something to do with the breakthrough that made her famous.

- Who? - Stella Drew.

Prescription sleeping pills...

found in Martha's bedroom with your name on the bottle.

You knew she was doubling her dose,

so you knew she'd sleep soundly while you murdered her husband.

Doctor Drew?

Over 35 million people are living with Alzheimer's today.

That's 35 million people fading away.

Martha figured it out, didn't she?

She confronted you in her kitchen,

you grabbed a knife and you stabbed her.

It's not just people with the disease who suffer.

It's their families, their children

who have to watch this awful decline.

Why did you murder Professor Seager?

Was it because he killed Soo-Min or because he knew that you had?

No, Richard didn't kill Soo-Min - neither of us did.

It was an accident. Yeah.

An accident which enabled you to steal lab work from her file

and pass it off as your breakthrough.

We found a back-up on a disc.

It was my doctorate. Soo-Min was my research student

so anything she stumbled across was mine to publish.

That's what Soo-Min failed to grasp.

She was threatening to take the findings home with her

for her own post-grad, so Richard and I went to talk some sense into her.

Tell us about this accident.

Eventually we found her, in the organ loft, collecting up her music.

She refused to have a sensible discussion.

She tried to leave, Richard was holding on to her...

..and after that... I don't know.

Suddenly she was... falling and there was this crack.

If it was an accident, why didn't you call an ambulance?

I was going to, but he stopped me.

He said if he went to prison, it would all fall apart -

the research, my post-doc funding, everything we'd been working for.

So I let him do it... I let him hide the body.

And then when he cut himself on a nail in the attic, I took over.

And then I lived with it. Every day for 15 years.

Until I realised it wasn't over -

it was all just the catalyst for everything else.

What do you mean?

Six weeks ago, Richard sent me the most extraordinary letter.

Three pages of waffle about God and the prison chaplain.

And then...

..this one paragraph at the end casually blowing everything apart.

Warning you he was going to confess?

He was going to betray me.

After 15 years of telling myself that if I worked hard enough,

if the research could make enough difference,

then what happened to Soo-Min might not be in vain,

he was pulling the plug on it all.

So you stole his car keys, you lured him outside,

and you killed him, framing Rachel.

But going to prison means abandoning my research and I can't let that happen.

I have a responsibility to see it through.

Was it your responsibility to kill your mentor?

And his wife when she figured it out?

Martha was my best friend.

That's the hardest sacrifice I've ever had to make.

But she said she was going to the police and...

Stella Drew, I'm arrest- Wait!

If you're going to arrest me, you need to understand...

my research isn't just some science project.

This is work with genuine potential.

It could make a difference to millions of lives.

If... if I go to prison, you're setting that back by decades.

I'm sorry, we're police officers.

Decisions about the future of mankind

don't really feature in our job description.

Stella! Stella!

Stell? What's happening?

I heard you were home. I wanted to see how you are.

And let you know that someone has confessed.

Where did you go? I dunno. I just walked around.

She'll be OK, though, won't you? It just takes time, that's all.

How can you keep making out you're sorry,

when you were so jealous of him

you faked a fall just to get some attention?

Yeah. I knew.

So leave it, OK?

Well, there you go.

First my husband left... then Erin.

It's just me and Rachel now.

Got what you came for?

They were erm... clearing out Adam's room in college,

returning things to his parents.

I thought you might like these.

Oh.

Thank you.

For taking the time. Thank you.

She all right? I think so.

Are you all right?

Surely you're not buying into all that stuff

about the future in dementia?

Stella Drew's not the only person working on it, you know.

It's not that.

I took your advice.

Got a meeting with Innocent tomorrow morning.

Oh, well, that's good.

That's really good.

I know you hate jumping through hoops...

It's not to talk about promotion.

It's to hand in my resignation.

Your resignation?

What's brought this on?

This job makes you look at things differently, doesn't it?

I always told you it would. Oh, I know.

I didn't understand. I don't like what I've become.

I used to think that people were... basically good.

Now I don't and I don't know when that changed.

Well, that's just a sign that you're a seasoned copper,

it's not a sign you should chuck it all in.

Well, you love this, you're still getting out.

Yeah, I think so, before too long.

But I've got to that stage. I've got to that stage too - earlier.

I've got a feeling that's not what the fast track scheme's all about.

Are you sure about this?

I need a change.

Well, in that case, I need a drink.

Come on.

What? Nothing.

We can... still meet up for the odd pint, can't we?

Two ex-coppers? Of course.

They do a pensioners' special on a Tuesday. I could treat you...

Oi, I'm still your boss for now.

I hope you don't feel it's been a waste,

being my boss... training me up.

Because I've appreciated it.

It wasn't a waste. It was a pleasure.

Thank you, sir.

You're all right.

And it's Robbie.

Thank you, Robbie.

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