THERE WASa gap of half a metre between the rafters I was lying on and those overhead. It wasn't much, and it made life very uncomfortable, but it was more than I'd expected.

Stretching out flat, I listened for sounds of pursuit in the cell below. There weren't any. I could hear people colliding with each other and barking out orders in the corridor, so either the police weren't aware I'd broken out, or had found their way blocked by the panicked crowds.

Whatever the answer, I had time on my side; time I hadn't bargained for, which I could put to good use. I'd planned to flee as swiftly as possible, leaving Mr Crepsley and Harkat behind, but now I was in a position to go and look for them.

But where to look? The light was pretty good up here there were many cracks between the plaster tiles, and light seeped up from the rooms and corridors below and I could see for ten or twelve metres whichever way I looked. This was a big building, and if my friends were being held on another floor, I hadn't a hope in hell of finding them. But if they were nearby, and I hurried …

Scuttling over the rafters, I reached the ceiling of the cell next to mine, paused and cocked my ears. My sharp sense of hearing would detect any sound above that of a heartbeat. I waited a few seconds, but heard nothing. I moved on.

The next two cells were empty. In the third I heard someone scratching himself. I thought about calling out Mr Crepsley and Harkat's names, but if there were police in the cell, they would raise the alarm. There was only one thing for it. Taking a deep breath, I gripped the rafters on either side with my hands and feet, then punched through the thin material of the ceiling with my head.