Adam Capstone, Professor of Geometric Topology.
The bomb was made out of fulminating mercury.
Cheated on you?
Paula Guitteau, she was one of his students.
- She committed suicide. - I wish only bad things for Adam Capstone.
He made me promise not to tell anyone who the father was.
Then Elizabeth found out about the payments.
So Elizabeth knew? She wouldn't have any problem getting mercury.
And she'd know what to do with it.
They were letters -- nothing else. I wanted to make him hurt.
Mr Adomakoh is one of our brightest stars, all the way from New York.
There wouldn't have been a breakthrough if not for me.
If their research can make a difference when I'm gone...
- A legacy. - I'd do anything for Donald.
Always remember 060302.
Put it down. Very slowly.
(Sirens blare)
GRACE: Mummy!
Mummy!
Your daughter needs you.
Are you OK?
Getting there.
At least he's alive.
How are you doing?
- Superficial bruising. - Yeah, me too.
How's your hearing? Mine's rubbish.
It's like being underwater.
What?
I said how... Very funny.
Have you called Laura?
She's not picking up.
I left her a message. Oh, God.
What were you thinking?
Well, we didn't exactly have a plan, sir.
You should've retreated and let the bomb squad take over.
And to hell with David Capstone?
I don't like my men being blown up.
- I'm not a huge fan of it myself. - It's because he cares.
So what did they say about Capstone?
He'll live.
- He's lucky. - I think you all were.
(Sighs)
Ow!
Well... I think um... I'll leave you guys to get on with it.
What was that for?
For putting yourself in harm's way.
- And that one's for the message you left. - What was wrong with it?
"I'm OK, it was only a small bomb"?
Well, it WAS only a small bomb.
Oh! Idiot.
Hey...
Listen...
.. I'm not gonna go to New Zealand.
But we're all set.
Yeah, I probably should've said something sooner but I...
I know it's a long way and it's my family and not yours...
- That's not it. - And the place'll be full of baby stuff...
I'm scared, Laura.
If I go now, I'm not sure there'll be anything for me when I come back.
Of course there will. Moody won't sack you when you're out of the country.
That's exactly what he might do. Anyway, he doesn't have to sack me.
I'm a consultant. All he has to do is not renew my contract.
Which will be very easy if I've been away for a while and people have forgotten I exist.
Well, what am I meant to do? Go on my own?
(Sighs)
We planned this together, Robbie. It's a trip of a lifetime.
And it will be.
- This is ridiculous. You're being ridiculous. - What if I'm not?
No-one's gonna forget you, Robbie.
Yeah, I've seen it happen.
Would it be the end of the world if it did?
This... This is what I know.
This is who I am.
I tried being away.
I'm rubbish at it.
This is what I do.
It's what I want to do till the day they carry me out of here.
Like Morse?
Well, there are worse ways.
I'm sorry, love.
I know you are.
Sorry to disturb...
Go. Be brilliant.
Sorry, Lizzie. What were you saying?
Good news. We got lucky.
Part of the package that the bomb came in survived the blast.
We know where it was posted.
- 11:43 yesterday morning. - Is this the best we can do?
Afraid so.
We've got a time and place. Let's see where everybody was.
Starting with Frank Guitteau, our letter writer.
How could I send it? I was at work.
Not at 11:43, you weren't.
According to your boss, you were out alone all morning.
I had a pick-up, office furniture out near Marston. You can check.
We did. They confirmed you left at 10:15. You weren't at the depot until after midday.
Which gives you plenty of time to have posted that parcel.
Did David Capstone know Paula well?
I don't know.
I mean, she probably attended his lectures.
But she didn't go to any of his tutorial groups or anything.
And when she accused Adam of rape?
He stuck by his brother, of course.
Like everybody else, just when Paula needed some friends.
And you resented him for that, did you?
So I wanted to blow him up, is that right?
Did you?
Of course not.
When can I go home?
(Church bell chimes)
Kate?
- I've got a few questions for you. - Well, can't it wait?
Er... no. Not really. Inside?
(Sighs) OK.
Well, er... how can I help you?
I wondered if you would mind telling me where you were yesterday morning.
What, you asking me for an alibi or something?
Er... OK.
I was in a lecture until 10:30.
And then I worked on a problem with the 3-D printer.
Mr Adomakoh.
I've left you a message.
Er... yes. I was busy. Sorry.
I was just leaving.
I saw you earlier, didn't I?
Outside David Capstone's house.
Er... yes. I was running. My route took me past his house.
I was interested.
Where were you yesterday?
Why are you asking him that?
- At lectures. - All morning?
Professor Mowbray likes to take his time.
And did anybody see you?
I don't know. You'll have to ask.
Yeah. I will. Thank you.
And if I've got any more questions, then I know where to find you now, don't I?
Why try to kill both brothers?
Well, the first bomb was pretty clumsy.
There was no guarantee he'd get Adam. It could have just as easily blown up his secretary.
There was no danger of that with this morning's effort.
I phoned Elizabeth Capstone. She said Adam often didn't even go in to work until gone 11.
Left all the admin to David.
So you're saying that Adam was a mistake and that David was the intended target?
Well, two bombs in three days.
Someone wants whoever dead in a hurry.
- What? - Come on.
David Capstone's just about to cash in on years of research.
Apart from his brother, who else would hate to see it happen?
- The person who saw it as their legacy. - Mm.
(Knock at door)
He's having a bad day.
Oh, you're wasting your time and mine.
We think Adam was killed by accident and David was the bomber's intended target.
What's that got to do with me?
You'd invested all that money for the greater good.
And David's selling to the highest bidder.
When you thought you'd leave something worthwhile behind.
- Did you try and stop him? - Oh, sure.
I threw together a parcel bomb because dexterity is one of my strongest points.
I wrapped it up, put on a stamp, went into town and posted it.
You could've had help. Where were you yesterday morning?
No, leave her out of it. (Coughs)
It's OK. Er... I was out yesterday morning, running errands.
- What sort of errands? - That's enough! I want you to go now.
In a moment. Ms Alderwood?
To the bank and then the shops.
Will you leave! Out!
(Coughs violently)
What was it you said? You'd do anything for him?
Can you think of anybody that would want to hurt you, Mr Capstone?
I'm assuming it was whoever sent those threatening letters.
Well, we believe those were directed at your brother.
Then, no. Sorry.
What about Kate McMurdoch?
Er... well, it's possible, I suppose.
I mean, I was the one who brought her in. I was her mentor.
I was the one who had to explain to her the um... realities.
Plus she had a sense of entitlement a mile wide.
Sorry, I...
It's been a long day.
Can we give you a lift home?
Or is there somewhere else you'd rather go?
No, no. I just want to go home.
Um... I would invite you in...
We need to be getting back.
Well, there is just one other thing.
You said you didn't know Paula Guitteau. Yet you marked some of her papers.
I marked one of her papers when Adam was away. But I didn't know her.
Er... that was at a Christmas party. I think the whole faculty were there.
I don't remember that, but then I was probably in 100 selfies that evening. Sorry.
Do the numbers 060302 mean anything to you?
Are they important?
We found them at Paula Guitteau's home.
A combination or something?
- Well, if you think of anything... - Yeah. Of course.
Er... Inspector?
You wait here.
He promised me money and then he went back on his word.
I knew where he kept it and I thought the house would be empty after what happened.
- Why did you need money? - I have debts.
What sort of debts?
Gambling.
I developed a taste. It's so easy.
You have no idea.
- David Capstone said he'd pay them off? - That's right.
We're a team, although the other players think that we're strangers. We play the casinos.
London, Birmingham, Manchester, once.
And most of the time, we win.
I thought the casinos did most of the winning.
Not if you cheat.
That's the lot. Are you OK?
I'm fine.
There is one thing.
The drawer.
Donald...
For everything you've done.
- I don't know what to say. - Don't say anything.
Just think about it.
A little security.
For Grace, obviously. I couldn't care less about you.
David would watch the cards being dealt, memorising who got what...
.. calculating the odds of getting a particular card next, and then he'd tell me.
- How? - Code.
He seems to be talking gibberish... his wife, how he's gonna buy a car.
From what he can see, David calculates the optimal play for any situation.
And then he adjusts it so as not to look suspicious.
He's got over 1,000 plays in his head.
He runs the game and no-one realises.
And afterwards, you'd divide the winnings?
- 70:30. - Except you wanted more?
Well, why not?
He made enough out of me.
Well, being refused, desperate, I can understand you'd resent him.
And you know how to fulminate mercury.
Except I didn't.
That wasn't me.
Where were you around 11:40 yesterday morning?
I was lecturing second years, about 40 of them.
The lecture ended at midday.
The day before Adam Capstone was killed, where were you?
I was er...
I was lecturing in the morning. I had a tutorial group in the afternoon.
And then I was playing blackjack in the evening.
- Alone? - With David.
I didn't tell you because at the time it didn't seem important.
I assumed the bomb was for Adam.
- What did it matter what my plans were? - It might matter a great deal.
Andrew Dimmock told us about the blackjack.
How well do you know him?
Er... I don't, not really. I met him at a college dinner.
I thought he'd be useful when I was looking for a partner. Doesn't look like a pro, see?
He blames you for his gambling debts.
I led him to water, but I didn't make him drink.
But it's never the fault of the addict, is it?
What's gonna happen to him?
Do you want to press charges?
No, he's got enough problems as it is. I don't want to add to that.
(Doorbell)
Excuse me.
Mrs Capstone.
Elizabeth was just checking up on me.
I was worried.
They're my Borromean Rings.
I had them printed on the 3-D printer the other day.
Three interlocked rings. But no two of them are linked.
If any is cut, it disintegrates.
Intriguing, isn't it?
My favourite knot.
I read somewhere that they were a symbol of love.
Two rings, separate, held together by something... other.
Without it, everything falls apart.
That's a bit sentimental, isn't it? Who came up with that?
I'd say the recipient of an arts degree.
So what did you make of Elizabeth Capstone showing up like that?
Natural concern for her brother-in-law?
No, I didn't think so, either.
As Adam Capstone's widow, she stands to benefit from the deal
with the drug company going through, right?
So she bumps off her husband who gets in the way of the deal who is also cheating on her?
Sort of two-for-one.
But why kill him before the deal has gone through? That doesn't make much sense.
We just need to work out the twist and writhe, that's all.
Twist and writhe?
The particular set of moves that'll unpick a given knot.
I'm getting bloody sick of that thing.
(Mobile rings)
Hello?
OK. Um... thank you.
That was the care home. Dad's taken a fall.
(Birdsong)
(Door opens)
I got him a newspaper and some magazine about trout fishing.
You just missed the doctor.
I thought he just bruised his hip.
Hey, Dad. It's me.
I've brought you a few things I thought you might like.
You should... You should stop wasting your time selling dusters and rubber gloves.
Get yourself a proper job.
They say he's had a series of mini-strokes.
Now piss off. I want to watch the cricket.
Are Forensics back from the scene?
Yeah, they found mercury from the blast.
Also sulphur, lime and magnesium.
- Almost certainly from the detonator. - That's a lot of chemicals.
Which could easily be accessed by Kate McMurdoch's boyfriend.
Djimon Adomakoh. Chemistry student.
Claims he was at a lecture when the second bomb was posted.
Only, he wasn't?
I can't find anyone to vouch for him. At least, not yet.
What do we know about him?
Er... foreign student.
He lives in New York. Family are originally from Ghana.
He is the star of the year.
He's already been offered a post-grad research fellowship.
We think he and Kate McMurdoch might be working as a team.
She blames David for stealing her research, kills Adam by mistake?
But she already knew David's home address.
If she was gonna kill him, why send the first bomb to the Maths Department?
I've got the Guitteau phone records here you asked for.
All these are landlines to Deermarsh Prison.
Why?
Apparently Joyce Guitteau has been visiting a right-to-lifer there -- George Jensin.
- I remember him. - Yeah.
The last time was four days before Adam Capstone died.
What's this Jensin bloke in for?
He sends bombs.
Yes, I went to see Gordon.
I'm a prison visitor. It's one of the charities I support.
She sees a lot of prisoners. So what?
They don't all know how to make bombs.
Gordon Jensin hasn't got any friends or family.
He's not a hardened criminal.
He's alone and scared and I visit him because no-one else will.
Do you honestly think we spend our hour discussing how to make bombs?
Can I ask where you were around 11:40 the day before yesterday?
- Why? - We know what time the second bomb was posted.
You couldn't pin it on me so you're having a go with her? Is that how it works?
Please just answer the question.
You lot failed my daughter when she really needed you.
And then you go and let a guilty man free and then stand by while we pay the price.
You're angry, I understand.
All you've got is supposition and coincidence. What gives you the right to...?
YOU have motive! You sent those letters.
You had access to mercury.
Your wife knows a convicted bomb maker.
Please...
I'm sorry.
But there's a man dead.
There's another man nearly died.
So, yes, I have the right.
I was at the hospice.
You can check.
They'll vouch for me.
Thank you.
So, I've checked and the lecture that day only lasted for an hour.
Not the whole morning, like you said. Where were you?
I went to go and get something to eat.
From where?
There's cafes round the corner.
- Is this your family up here? - Yes.
- They must be very proud. - I hope so.
- How long have you and Kate been together? - Two-and-a-half years.
That's very impressive.
Most student relationships only last two-and-a-half months.
Yeah, but not in this case.
(Door closes)
Frank?
Don't cry.
I just want this feeling to... stop.
It will, love. Soon.
I promise.
(Sobs)
I'm so sorry.
For everything.
Never think I blame you.
(Yawns)
He's asleep.
Maybe you should get some, too.
- No, I'm all right. - Liar.
So what's the plan? Keep him here?
For now.
Moving him'll only make him more confused.
(Exhales)
Will you stop by later?
Well, there isn't any point, is there?
I think there is.
He doesn't know who I am.
I wasn't talking about Dad.
He is running out of teeth to lie through.
First of all, it was the lecture. Then it was the cafe.
- He wasn't there either? - For about ten minutes, according to the owner.
But not for the hour and a half that he claims.
So what's he hiding?
He's besotted with Kate McMurdoch. He'd do anything for her.
What, like make a bomb?
In a heartbeat, I reckon, if she asked him.
Don't forget, these two work in the same department.
So does she.
Maybe we're looking at this wrong. Maybe it's nothing to do with Djimon and Kate.
Something else bothers me.
In his room, he's got pictures of his family all over the wall.
- His mum, dad, brothers, sisters... - Well, he's a long way from home.
Exactly. So you'd think that at least one of them would feature New York. Not one of them does.
So I've checked his phone records.
He has not sent a text or made a call to the US in the whole time he's been here.
Not one.
♪ JOHANN STRAUSS: Rosen Aus Dem Suden
(Door opens)
Sorry, sorry.
I had to go out. Spur-of-the-moment thing.
Here, let me help.
- I thought you were sleeping. - I was.
Massive blast trauma to the head, I'm afraid. It blew up in his face.
It blew up while he was making it?
Well, I'll know more after the post mortem, but I'd say so, yes.
Why wasn't I called?
I thought you were with your dad.
- Well, I should be here, shouldn't I? - You should be there.
We can cover this.
Go. Hold his hand.
We don't do holding hands.
At least I'm leaving you with an interesting one.
Something to keep you busy while I'm gone.
Why? What've you found?
Andrew Dimmock wasn't blown up. At least, that's not how he died.
When you're killed in an explosion, you get severe pulmonary contusion --
bleeding and swelling around the lung, "blast lung".
If the bomb doesn't kill you outright, blast lung will finish off the job.
And he doesn't have that?
Plenty of external damage, some penetrating trauma,
but no injuries associated with inhalation of any kind.
But... his hyoid bone was fractured.
There may be some bruising which hasn't developed yet,
but even so, I'd say Andrew Dimmock was strangled.
I've booked a taxi for tomorrow.
It's picking me up at nine.
Well, I can take you.
You've got work to do.
And I'm not very good at airport goodbyes.
Well, there must be something I can do?
You can sit on my suitcase, help me close it.
I'll see you later.
- (Sighs) - So you've decided not to go?
That's right.
That is your decision?
Come on, then. Spit it out.
No, I was just wondering why you changed your mind.
You were keen. I'm wondering what's happened.
Nothing's happened.
Well, if it isn't something that's already happened,
then it's something that you think will happen.
Have you quite finished?
You're worried that if you go, Moody'll close you down.
Rubbish, man.
You'll come back and you won't be a copper any more.
And if you're not a copper, what will you be?
- Shouldn't I be lying on a couch for this guff? - Do you love Laura?
Then go.
Show her that you love her.
Don't assume she knows. People make that assumption and it's a mistake.
Still. Your decision.
Sorry. I've checked Djimon Adomakoh's immigration status.
Don't tell me. Illegal?
No, no, his visa's fine.
But according to Border Control, Djimon Adomakoh isn't even in the country.
He flew back to the States nine months ago.
- Bring him in. - OK.
I'm sorry if I overstepped the mark.
- You're over-reacting. - I won't let them destroy us.
They can't.
- I told you, we just wait. - We are past that now!
We have been for a while.
Whoever it was, they almost certainly knew Andrew Dimmock.
- Because...? - No sign of a break-in at the lab.
So either he let them in or...
They had their own key.
Why him?
Sorry?
All these suspects.
Why pick Dimmock to frame?
Because it creates a narrative that we'll follow when it comes to the ready-made motive.
So which of them knew that?
Well, Elizabeth Capstone worked in the same lab as him.
He knew Donald Lockston socially and, by extension, Sarah Alderwood.
Kate McMurdoch didn't know him and Djimon Adomakoh did.
Sergeant Maddox is picking him up now.
You see, all along, the killer's been hidden. Everything's happened at arm's length.
But yesterday, for the first time, they had to be at the scene to frame Dimmock.
They had to show themselves.
- Where are you going? - I'm going back.
This time the killer's been forced out of their comfort zone.
- So maybe, this time they've made a mistake. - I'll come with you.
No, I'm fine on my own.
Tell me about Djimon Adomakoh.
My name is Joseph Donadu.
I live in Ghana.
When I was a kid, I used to look at photos of Oxford.
I know all the names of the colleges and landmarks.
After school, I used to work in the evenings so I could sit my A Levels.
And when I got the grades I needed, when it meant I could come here and apply...
someone in the Foreign Office or the Home Office
decided that they didn't want a kid from Ghana studying chemistry.
Something about all that knowledge being used dangerously, I suppose.
So my visa application was refused.
Too bad, eh?
But I'd worked too hard to just...
So you impersonated someone else?
My cousin, Djimon. He lives in America.
There's no restrictions, see.
He applied instead?
And he came for the interview.
It worked brilliantly.
Until you got offered the post-grad research position.
I needed Djimon to come back so I could extend my visa.
That's why I lied about where I was.
They will send me back home, won't they?
Yeah.
Yeah, I expect so.
You know, all I wanted to do was learn. That's all I wanted to do.
But instead, I met...
I thought not getting a degree was the worst thing that could happen.
I was wrong.
(Glass crunches underfoot)
(Door opens)
Fresh pair of eyes?
Djimon Adomakoh is not the bomber.
He's not even Djimon Adomakoh.
Fake ID for a student visa.
Anything?
Maybe. These are the forensic reports for the three bomb blasts.
At David Capstone's, there were traces of calcium hydroxide and sulphur.
But not the other two. Why do you think that is?
Maybe the bomber used a different detonator?
Right. I'd better get Djimon's arrest report written up.
Calcium hydroxide's another name for lime.
Sulphur and lime.
You think that's true?
"Work alone is noble"?
Bit outdated, isn't it? Being noble.
I'm not sure I even know what it means any more.
Yeah, you do.
- There's nothing here. - Probably not.
Sir?
(Sighs)
Along with the usual paraphernalia,
it's useful to have a mercury spillage kit which contains sulphur and lime,
which reacts with the mercury and stops it rolling about.
(Mobile rings)
- Yep? - 'James?'
060302. I know what it means.
- I know who sent that card to Paula. - Me too.
I told the cab to wait.
What do you think?
Very distinguished.
Understated elegance with a hint of boffin.
(Giggles) Bull's-eye.
- (Door bell) - Oh, I told him we'd be a few minutes.
Mr Capstone?
Can this wait? We're announcing the deal with AKGC Pharma this evening.
No, sir. I'd like to do it now. If you'd excuse us?
I've got nothing to hide.
Were you in love with Paula Guitteau?
Don't be absurd.
"Always remember. 060302."
- That's what you wrote to her, isn't it? - I'm sorry?
632.
The link symbol for the Borromean Rings.
Your favourite knot. Also your little in-joke with Paula.
I told you. I barely knew her.
Two rings, unconnected, held together with a third?
Without it, everything else falls apart.
You were in love with her.
I think I'd like you to leave.
Just like her parents, you held your brother responsible for her death.
And you all wanted revenge.
The difference was, they sent him angry letters. You sent him a bomb.
And your proof? The rings are well known. Anyone could've sent that card.
Who said anything about a card?
Adam wasn't the intended victim. I was.
Dimmock killed the wrong person and tried to put it right.
No, that's what you wanted us to believe.
After all, how could you be the murderer if you were also the intended victim?
I'm sure you intended to set off the second bomb here once at a safe distance.
Then you heard we wanted to talk to you,
so you waited till we arrived and used us as witnesses.
You promised to pay off Andrew Dimmock's gambling debts if he procured mercury for you.
And then, later, the sulphur and the lime needed to clean up after one of your spillages.
The more desperate he became, the more of a danger he posed.
He was a loose cannon. You had to shut him down.
So you gave us the murderer, killed by his own bomb.
Except he wasn't, was he?
You strangled him, and then tried to frame him.
David?
Tell me they're wrong.
Adam always said you used to bear grudges.
Even as a kid -- store it up, let it fester.
- That's nonsense. - What's the matter?
Didn't like baby brother being cleverer?
- No. - Better looking, more successful.
- What, you think I was jealous? - Then why?!
Because of Paula!
I... I thought...
.. finally...
.. someone I could share a life with,
something good, that was mine.
But Adam couldn't...
.. he had to spoil that, too.
He told her about the gambling, made it seem grubby, like I had a problem.
I tried to speak to Paula after that but she wouldn't listen to me.
She was so ashamed. And then she...
He broke the only thing that mattered to me, because he could.
My brother.
What am I gonna do without him?
It'll still be here when you get back.
That's what I'm afraid of.
I've got something for you.
What do you think?
Thank you.
It's perfect.
- The Dodo? - Famous Oxford icon.
And a bird that I can relate to.
- Except you're not extinct. - Well...
let's hope that's still the case when I get back...
.. from New Zealand...
.. where I will have been with you.
If that's OK.
I think I've been a bit of a fool.
Well, actually, I've been a lot of a fool.
And I'm really sorry.
I'll make it up to you, I promise.
And I won't forget.
Yeah, you will.
- But I'll remind you. - (Chuckles)
Robbie. Demob happy?
- Something like that, sir. - I would never have caught that knot clue.
But you did.
Sir.
Have a safe trip. See the sights, recharge your batteries.
I need you match-fit if you ever want to come back.
Thank you, Joe.
(Sighs)
I came to say goodbye.
Aw. It's not gonna be the same without you.
Ah. Do you fancy a drink?
Oh, um... I can't. Er... I've got a girls' night.
We're celebrating. Tony's decided to take the job for another year, so er...
- Yeah, it's good news. - And you're happy?
Oh, yeah. Yeah. No, it's...
It's brilliant.
Is James around? I'll say cheerio.
No. No, he's gone for the night.
- Ah, well, not to worry. - Give him a call.
Nah. It's not important.
Well, don't... Don't forget about us.
"For Christ plays in ten thousand places.
Lovely in limbs, and lovely in eyes not his
To the Father through the features of men's faces."
The taxi should've been here by now.
I thought they were reliable.
They are.
I'm gonna get something to read.
For talking him round.
Long flight.
Nearly 24 hours.
Worth it, though.
Have to get there, first.
You'll be missed.
I'd better be.
Have fun. You deserve it.
So do you.
You have to get there, first.
OK?