“Wonder how easy it was for him to get in,” Siobhan said quietly. Her words reverberated in the silence and a head appeared around a door halfway down the corridor.

“Took you long enough,” boomed the voice of DI Bobby Hogan. “Come and have a look.”

He had retreated back inside the sixth-year common room. It was about sixteen feet by twelve, with windows high up on the external wall. There were about a dozen chairs, and a desk with a computer on it. An old-looking hi-fi sat in one corner, CDs and tapes scattered about. Some of the chairs had magazines on them: FHM, Heat, M8. A novel lay open and facedown nearby. Backpacks and blazers hung on hooks below the windows.

“You can come in,” Hogan told them. “The SOCOs have been through this lot with a fine-toothed comb.”

They edged into the room. Yes, the SOCOs-the scene of crime officers-had been here, because this was where it had happened. Blood spatters on one wall, a fine airbrushing of dull red. Larger drops on the floor, and what looked like skid marks from where feet had slid across a couple of pools. White chalk and yellow adhesive tape showed where evidence had been gathered.

“He entered through one of the side doors,” Hogan was explaining. “It was break time, they weren’t locked. Walked down the corridor and straight in here. Nice sunny day, so most of the kids were outside. He only found three…” Hogan nodded towards where the victims had been. “Listening to music, flicking through magazines.” It was as if he were talking to himself, hoping if he repeated the words often enough, they would start answering his questions.