She shrugged, clopping in faded pink Crocs towards the back door. Opened it, looked at him: she expected him to follow.

Into the hot airless cave that was their little brick house.

‘He’s asleep,’ she said. ‘You know where.’

She left him there in the kitchen. A door slammed. Presently, he heard squeaky taps and shower water drumming against a plastic curtain. Taking a breath, Hirsch walked through to Daryl Cobb’s battered door and knocked and waited. Knocked again, a hard, knuckling rap. Tough guy, he thought self-consciously, and decided simply to walk in.

The boy was asleep, wearing only boxer shorts, a big, soft, downy creature beached on a grimy sheet, his feet tangled in the top sheet. The room stank: sweat, dope, the rancid smell of unwashed flesh and clothing.

Hirsh regarded him glumly. Meanwhile Laura finished showering: he heard the water stop, the curtain rings clack. A quick towel rub later, her bare feet padded to her bedroom and a door slammed. Hirsch sighed again. Back to Daryl.

His footwear first: runners, black pointy-toed going-out shoes, thongs. No blood. The clothing on the floor, the chair, in drawers and the wardrobe. No blood.

Hirsch re-entered the hallway just as Laura emerged from her bedroom, her hair dampening the neck and shoulders of a yellow T-shirt, her legs thin and vulnerable in a baggy pair of shorts. ‘Quickest shower in history,’ he said.

She ignored him. Banged out of the back door and, a moment later, he heard her bicycle wheels.

The laundry next. The washing machine was bone dry. White knickers, a black bra and a Redruth High School summer uniform in the dirty-clothes basket.

But the absence of bloody clothing and footwear wasn’t proof of Daryl’s innocence. Hirsch took out his iPhone and replayed the video. He finally spotted Daryl near the end—with his sister, and his mother, cheering as Nan reached up to Santa for her Best Christmas Lights certificate and plum pudding. He was wearing blue boardshorts and a Kings of Leon T-shirt.

Hirsch returned to the bedroom. The T-shirt and the shorts lay where Daryl had stripped them off. Hirsch toed them open again: no blood.

It didn’t mean anything. The kid could have changed his clothes, killed and slashed a few horses in the darker hours, buried his bloodied clothing in the backyard.

‘All of them?’ asked Daryl Cobb dazedly.

‘Four dead,’ Hirsch said. ‘Couple more with stab wounds.’

He’d dragged two of the sticky kitchen chairs out into the sweeter air of the backyard, and now he watched Daryl stare at Laura’s tomato plants as if answers lay among them. The boy’s befuddlement might owe something to being hauled out of bed and plonked on a chair in the great outdoors hours before he usually awoke, Hirsch thought, but it owed a lot more to the enormity of the crime. The kid was staring vacantly, slack-jawed, unable to take it in.