‘This is exactly the sort of reaction Billy was hoping for,’ he said. ‘He’s deliberately staying out late to make you worry. Then you’ll be relieved, not pissed off, when he finally gets home.’

Jake’s comment seemed to reassure Mark but I wasn’t convinced. Billy wasn’t that manipulative. There was no way he’d put me through the wringer to punish his dad and, as the living-room clock ticked from midnight to 1 a.m. I became increasingly frantic, insisting that Mark drive round with me to try and find him.

‘I will fucking kill him when we find him,’ he muttered as he fitted the keys into the ignition. ‘I need to be up for work in five hours’ time.’

We drove round and round, stopping at all Billy’s known haunts – all the parks and the underpasses where he’d practise skateboarding with his mates – and everywhere else we could think of where a fifteen-year-old might shelter from the bitterly cold wind that had caught my skirt and wrapped it around my calves as I’d climbed into the car: bus stops, McDonald’s restaurants, the train station and the doorways of the cinema and bowling alley in Avonmeads.

‘I bet he’s kipped down for the night on a mate’s sofa,’ Mark complained as I insisted we drive around Knowle and Totterdown one last time. ‘Probably one of those dossers he hangs around with. If he’s still not home by morning we’ll call the police.’

‘And if he isn’t?’ I could barely bring myself to ask the question.

‘Then the police will talk to everyone he knows and find out where he’s hiding. Claire, he’s fine. I guarantee it.’

He sounded so certain, so definite, that I agreed to ignore the knot of fear in my gut and go home.

Mark passed out the second his head hit the pillow. I lay awake beside him, ringing Billy’s number over and over again, finally passing out somewhere around 5 a.m., the mobile pressed between my ear and the pillow.

‘Is that a yes?’ Mark says now. The sharp tone to his question makes me clutch at the cushion. ‘You think I did something to Billy, don’t you?’

I want to believe that my husband would never do anything to hurt our children but you hear that all the time, don’t you, about men like that. ‘He didn’t look the type.’ ‘He was always so good with the kids.’ ‘They loved him.’