‘Maybe not,’ I said. ‘They’re young, these girls. If one of them saw something, heard something, she might not have copped what it meant; not at the time. Specially if it had to do with sex, or relationships. This generation know all the facts, they’ve seen the porn sites, probably they know more positions than you and me put together; but when it comes to the real thing, they’re miles out of their depth. A kid could see something and know it was important, but not understand why. Now she’s a year older, she’s got a bit more of a clue; something makes her look back, and all of a sudden it clicks together.’

Conway thought about that. ‘Maybe,’ she said. But the grim layer stayed put: not letting herself off that easy. ‘Doesn’t matter. Even if she didn’t know she had info, it’s our job to know for her. She was right in there’ – backwards flick of her head, to the school – ‘we sat there and interviewed her, and we let her walk away. And I’m not fucking happy about it.’

It felt like the end of the conversation. When she didn’t say anything else I started to turn towards the path, but Conway wasn’t moving. Feet apart, hands in her pockets, staring into the trees. Chin out, like they were the enemy.

She said, without looking at me, ‘I got to be the primary because we thought this was a slam-dunk. That first day, the morgue boys hadn’t even taken away the body, we found half a kilo of E in the stables, back of the poison cupboard. One of the groundskeepers came up on the system: prior for supply. And St Colm’s, back at the Christmas dance they’d caught a couple of kids with E; we never got the supplier, the kids never squelt. Chris wasn’t one of the ones who had the E, but still . . . We figured it was our lucky day: two solves for the price of one. Chris snuck out to buy drugs off the groundskeeper, some fight over money, bang.’

That long sigh again, above us. This time I saw it, moving through the branches. Like the trees were listening; like they would’ve been sad about us, sad for us, only they’d heard it all so many thousand times before.

‘Costello . . . He was sound, Costello. The squad used to slag him off, call him a depressing fucker, but he was decent. He said, “You put your name on this one. Mark your card.” He must’ve known then, he was gonna put in his papers this year; he didn’t need a big solve. I did.’

Her voice was indoors-quiet, small-room quiet, falling through the wide sunshine. I felt the size of the stillness and green all round us. The breadth of it; the height, trees taller than the school. Older.

‘The groundskeeper alibied out. He’d had mates round to his gaff for poker and a few cans; two of them kipped on his sofa. We got him for possession with intent, but the murder . . .’ Conway shook her head. ‘I should’ve known,’ she said. She didn’t explain. ‘I should’ve known it wasn’t gonna be that simple.’