There were many empty seats when school started again in the afternoon,and the teachers struggled against the mood of distracted restlessness. Adam felt the horrible excitement more than anyone. It ate away at him and made him feel almost physically ill. He had his own ideas about what had really happened, but as usual no one was interested in what he had to say. It was the guns that fascinated them most and there had been much technical discussion about Uzis and Mach 10s, Brownings and Glocks, but the others only scoffed when he offered his opinions. He felt as if he might literally explode with frustration at the familiar sense of insignificance, of being excluded.

Mr Pemberton was oblivious to it all. He was drawing a graph on the board, a sweeping curve just like that of the rail line. A parabola, he said. Nobody paid any attention.

The train tracks formed one curving side of a triangle of railway land bordered by the school wall and by the back fences of the warehouses along Mafeking Road. The walls and fences were too high to climb, and so this inaccessible little bit of wilderness in the middle of crowded inner London had become an island of mystery to the kids of Camberwell Secondary. There were stories of valuable things buried there, of stolen goods thrown from trains, and of strange animals in hidden lairs. Adam’s mind often turned to these stories when he lay alone in bed at night, imagining himself a hero, penetrating the mysterious triangle and making a stupendous discovery.

Now the coppers were on the railway land, searching with sticks and metal detectors along the border against the school and garage where the girls were found. They must be looking for the killer’s gun, Adam thought, possibly thrown over the back wall. The sight of them filled him with anguish. Suppose those probing sticks, those powerful detectors, found something else, another prize, the great prize-his prize.