There was a terrified yell as he fell towards me, and this turned into a laugh as he stopped outside the elevator entrance. He struggled for a moment to get out, missed his moment and fell back to the ground floor again with a yell. He didn’t get out there either, and fell back up to the tenth floor, where I grabbed his hand and pulled him in before he spent the afternoon falling backwards and forwards – as I had done when I first got here.

‘That was fun,’ he said, trembling with a mixture of fear and excitement. ‘What if I change my mind halfway?’

‘Then you go to whatever floor you want. It’s falling fast today. Must be the dry air.’

‘How does it work?’

‘It’s a standard Ambiguity enchantment – in this instance, the difference between “up” and “down”. Carpathian Bob left it to us in his will. The last spell of a dying wizard. Powerful stuff. You’ll be in Room 1039. It’s got an echo but, on the plus side, it is self-cleaning.’

I opened the door to his room and we walked in. The room was large and light and, like most of Zambini Towers, shabby. The wallpaper was stained and torn, the woodwork warped and unsightly damp patches had appeared on the ceiling. I watched as Tiger’s face relaxed into a smile, and he blinked away the tears. At the convent, he would have been used to sharing a dormitory with fifty other boys. To anyone else, Room 1039 would have been a hovel – to the foundlings of the Sisterhood, it was luxury. I walked across to the window and removed the cardboard covering a broken pane to let in some fresh air.

‘The tenth floor is fully teenager compliant,’ I said, ‘nothing will ever be out of place.’

To demonstrate, I moved the blotter on the desk slightly off kilter, and a second or two later it realigned itself. I then dug a handkerchief from my pocket and threw it on the carpet. As soon as it hit the floor it fluttered off to the top drawer of the bureau like a butterfly, folding itself as it went.

‘Don’t ask me how it works or who cast it, but be warned: enchantments have no intelligence. They follow spell sub-routines without any form of discretion. If you were to fall over in here you’d find yourself tidied away into the wardrobe, as likely as not on a coat hanger.’

‘I’ll be careful.’