He ran for the door. The only way forward beyond the threshold was the staircase leading up. It wound around the inside of the tower in an angled spiral, with only a flimsy-looking wooden handrail separating the stairs from the central bore. The platform at the top of the tower must have been at least forty metres in the air. Just the thought of being up so high made Fleet feel dizzy.

‘Christ,’ he muttered. ‘As if a burning building weren’t enough.’

He started to climb, and as he did so he heard a yell from above. He leaned out across the handrail as far as he dared, and caught a flash of movement somewhere near the top. There were two people pressed close together, and as the man at the rear happened to glance down, Fleet caught sight of his face. It was Isaac – Zack – and he was holding a knife that was still bloody from the wound he’d inflicted on Richardson’s bodyguard. When he saw Fleet following them, he shouted again, driving Callum Richardson on. It struck Fleet that it was probably only because the bodyguard had got in Zack’s way that Callum Richardson wasn’t already dead. Fleet had to hope that Bevan had got the man to safety, and that the stab wound wasn’t as serious as it had looked.

The higher Fleet climbed, the tighter he clung to the wall. He tried to ignore the void beyond the handrail, as well as his lungs clamouring for air.

Nicky, he reminded himself. You’re doing this for Nicky. And you’re going to make sure she realises what you went through just as soon as you know she’s safe.

There was an opening at the top of the staircase, and Fleet made it to the final flight of steps just in time to see a trailing foot disappear on to the platform beyond. He clambered up the last few stairs and out on to the platform himself.

‘Stay back!’ roared a voice. ‘One more step and I’ll cut his throat! I swear to God, I’ll do it!’

Fleet rocked back on his heels. It wasn’t just a response to Zack’s command and the knife pressed to Callum Richardson’s neck; it was the scene that had opened up before him. They must have been the equivalent of five or six storeys in the air, on a platform maybe seven metres square, the clock tower’s bell like a chandelier above their heads. All four sides of the platform were completely open, save for a stone pillar at each corner, and a perimeter wall that was knee height at best. Fleet had emerged on to the platform barely a metre from the edge. The front entrance to the school was directly below, all the people who’d escaped the chapel gathering together at the top of the driveway in a writhing mass.