The only person on duty at 4 a.m. that night is PC Akash Lockhart (father from Midlothian, mother from Southall). His sergeant was there earlier but went off at 3 a.m. so PC Lockhart is on his own till the morning shift comes on at 7 a.m. There’s usually very little happening at that hour so he is doing what all PCs do when there isn’t a sergeant or inspector around: he has his feet up on a desk and his head is lolling back against the top of the chair. His eyes are closed. He is nursing a cup of instant coffee between both hands, resting it on his stab-proof vest. He is thinking of a young woman called Veena who is betrothed to his cousin Randeep in Leicester and is, in his opinion, the most beautiful woman he has ever set eyes on. She is a dental nurse and even though he has never seen her at work, he thinks about her in her white coat all the time. In his dreams, the coat is always pristine and her long, glossy hair waterfalls down over her back and shoulders. At four o’clock this particular morning, he is thinking about Veena in her white coat and wondering if he will love her forever and dwelling on how embarrassing that will be, as he is destined to see her at family events for decades to come.

Then the phone rings and it’s Tom, saying breathily, ‘Who’s that? Who’s there? Peter?’ Peter Barker is the inspector. He and Tom are old friends and play together in a ukulele band.

‘No, it’s me, Akash,’ says PC Lockhart, even though he doesn’t recognise the voice on the other end of the line – he knows Tom by sight. ‘PC Lockhart, how may I be of assistance?’

‘Fatality on Seven,’ says Tom.

PC Lockhart is upright in his chair, slamming down his coffee cup with a force that makes the contents slop onto his desk. ‘Have you told Control?’

‘Yes.’

‘Good, okay, I’m on my way,’ Lockhart says.

Lockhart is out of his office in seconds and runs across Station Approach. Tom is waiting for him at the barriers, his face a mask of panic.

As he runs past him, Lockhart says, ‘Lock down the station, now!’

Tom nods.

Lockhart runs for the stairs, taking them two at a time. As he traverses the covered walkway he speaks into his radio mike and finds out that BTP officers from Milton Keynes and Nottingham are on their way – the Nottingham squad was already somewhere between Corby Glen and Market Deeping, for some reason, so they won’t take long, but Cambridgeshire Constabulary will still get there first. He snaps on his rubber gloves as he runs down the stairs to Platform Seven.