The eighth book in the Tom Thorne series, 2009

‘Come on, pigeon! Let’s go blow at the trains.’ Debbie Mitchell tugs at her son’s arm, but he pulls hard in the opposite direction, towards the chocolate Labrador the old woman is struggling to control. ‘Puff-puff,’ Debbie says, blowing out her cheeks. ‘Come on, it’s your favourite…’

Jason pulls away harder, strong when he wants to be. The noise he makes is somewhere between a grunt and a whine. Anyone else might think he were in pain, but Debbie understands him well enough.

‘Dog,’he says. ‘Dog, dog!’

The old woman with the Labrador smiles at the boy – she has often seen the two of them in the park – then makes the same sad face as always when she looks at his mother.

‘Poor thing,’ she says. ‘He knows I’ve got some treats for Buzz in my pocket. He wants to give him a few, don’t you?’ The dog hears this, pulls harder towards the boy.

‘Sorry,’ Debbie says. ‘We need to go.’ She yanks at Jason’s arm, and this time his cry is one of pain. ‘Now…’

She walks fast, glancing over her shoulder every few steps, urging Jason along. ‘Puff-puff,’ she says again, trying to keep the terror from her voice, knowing how easily he picks up on such things. The boy starts to smile, the dog quickly forgotten. He runs alongside her making chuffing noises of his own.

The dog is barking somewhere behind Debbie as she hurries away. The old woman – what was her name, Sally? Sarah? – meant well, but on any other day Debbie would have said something. She would have smiled, concealing her irritation, and explained that Jason was nobody’s poor anything. That there was no happier child alive, no child more cherished.

Her precious boy. Nine next birthday, with hair on his legs already and an extra-large Arsenal shirt. Who will almost certainly never be able to feed or dress himself.

‘Train,’ Jason says. Tries to say.

She hurries across the lower field, past the bench where they usually sit for a while, where they have an ice-cream sometimes in hot weather, then Jason runs ahead as they move on to the football pitch. They’ve been coming here for a couple of years and, as she hurries towards the familiar tree-line that borders the railway tracks, it strikes her that she doesn’t even know what the place is called; if it even has a name. It’s not Hampstead Heath or Richmond Park – there had been a flasher active for weeks the previous summer and sometimes the local kids lit fires at night – but it was theirs.

Hers and Jason’s.

She checks behind again and keeps moving. Walking, fighting the urge to run, fearing that if she does, someone will see and try to stop her. Seeing no sign of the man she’s watching out for, she picks up her pace to catch Jason. He’s stopped in front of the goalposts to take an imaginary penalty, same as always. He does it whether there’s a game on or not, and the boys who play here are used to seeing him charging on to their pitch and flapping around by the goal, waving his arms about like Ronaldo. Sometimes they cheer and none of them laughs or pulls faces any more. Debbie could kiss each one of the little sods for that. Brings them cold drinks now and again, or a few cut-up oranges.

She takes Jason’s hand and nods towards the bridge, a hundred yards ahead and to the left.

They move quickly towards it.

Normally they’d have come the other way, through the entrance opposite her own place, which would have taken them across the bridge on the way in. There would not have been any climbing on plastic chairs and scrambling over her friend’s garden fence.

But this was not a normal day.

When she looks around again, she can see the man on the far side of the football pitch. He waves and she fights the urge to shit herself on the spot. He couldn’t reach them in time, she thinks, even if he ran. Could he? The fact that he is just walking, though, the confidence in his easy stride, terrifies her more than she ever thought possible. Convinces her that she is doing the only thing she can. She had known even before she’d heard him talking on the phone. She’d seen it in his eyes and in the dreadful red stain beneath his jacket.

The man waves at her again and starts to jog.

On the bridge, Jason stops at his usual spot and waits for her, knowing that she will help him see the train when it comes. He looks confused when she moves to his side. He puffs out his cheeks and waves his arms.

There was a metal safety-barrier once upon a time, but bit by bit it had been pulled down, as soon as those with nothing better to do had covered every inch of brickwork with graffiti.

Who had shagged who. Who was a poof. Who had been there.

She puts a hand on Jason’s shoulder, then starts to drag herself up, ignoring the pain as her knees scrape against the bricks, and carefully inches her belly across the top. She takes a few fast breaths, then slowly lifts one leg at a time, up and over until she is sitting. She doesn’t dare look down; not yet.

She looks around to make sure that nobody is watching and it is then that she hears the voice of the real policeman. He is somewhere nearby on the far side of the bridge, coming from the other direction. His voice is cracked and raw as he shouts her name, and she can tell that he is running. He keeps on shouting, searching, but Debbie turns away.

Too late, she thinks. Much too late.

She reaches down to pull Jason up, her heart lurching at his smile of excitement. She’s always lifted him before, just high enough so that he can see over the edge, watch the train as it thunders beneath them.

This is a whole new adventure.

She cries out with the effort of hauling him up and fights back the tears as he settles down, dangles his legs and snuggles up close to her. He feels the vibration before she does, lets her know in a series of gulps and shouts.

Debbie feels her guts turn to water and looks up to see the train rounding the bend in the distance. The southbound Tube from High Barnet. She knows it will slow a little just before the bridge as it approaches Totteridge and Whetstone station. Still fast enough, though.

Debbie scrabbles for her son’s hand and squeezes. She leans down and whispers soft, secret words, knowing – despite any number of expert opinions – that he understands her. He points and yells as the train gets closer, louder. That smile that kills her.

Debbie closes her eyes.

‘Puff-puff,’ Jason says, blowing at the train.