But it probably will, thought Hirsch, gazing glumly at Brenda Flann’s wrecked car.

Feeling sticky, grimy and fatigued, Hirsch walked through to the highway and on to the Cobb house, hoping he’d find Adam Flann there with Daryl, the boys glued to an Xbox or watching a DVD. Ten minutes until the school bell sounded.

The Cobbs lived in a small 1970s brick veneer ravaged by time and the inland sun, sitting low in the dust as if waiting for further blows. No front garden, no decoration, no Christmas wreath, just weariness and stored heat. Marie Cobb was rarely seen in the town. Unemployed, chronically shy, she suffered from bipolar disorder and her children were her carers. If families like the Flanns were not uncommon, nor were families like the Cobbs, Hirsch had discovered in his brief career.

He set himself to knock, wondering who would answer. Daryl Cobb, seventeen, a big, soft, sloppy boy with a touch of ADHD, easily led by someone like Adam Flann? Laura, his younger sister? No: Laura wouldn’t be back from high school yet. She was the calm, practical, organised one. Did well at her studies and earned a few dollars after school grooming miniature ponies for a local breeder. That left Marie, who, in all probability, wouldn’t answer the door.

Hirsch rapped his knuckles, waited in the heat. The house seemed to grow tense, barely breathing, and he could sense Marie Cobb alone in there, either manic and afraid or depressed and asleep.

Laura would be home on the bus soon, but where was Daryl? Hirsch shrugged; nothing more he could do. With any luck, Adam had scrounged a lift home with someone, and would hear about his mother from Wayne.

He walked back to the police station just as the final bell sounded in the school on the other side of the road. Fished out his car keys and got behind the wheel of his ancient Pulsar just as the kids poured from their classrooms.

Ignition: nothing.

Flat battery.

‘Six fours,’ he was saying a couple of minutes later, behind the wheel of the police Toyota.

‘Twenty-four.’

‘Four sixes.’

‘Twenty-four.’

‘The square root of the third integer taken as a percentage of the hypotenuse.’

‘Three-and-a-half.’

‘I didn’t think you’d get that one, frankly,’ Hirsch said. ‘Very good.’

Katie Street touched her shoulder to Hirsch’s briefly. She was a wisp in the passenger seat, skinny legs, short dark hair damp on her neck. Wearing the Tiverton Primary School uniform of tan shorts and dark blue polo shirt. Scuffed sneakers with yellow laces propped on the dash, a massive backpack in the footwell. A solemn, watchful kid when Hirsch had first met her, but different around him now. A practical kid. She’d had some trauma in her short life, but seemed okay. No nightmares, no tendency to take a memory out and agonise over it. He didn’t think so, anyway.