‘Probably her office – third floor.’ Karim looks up as the lights flicker on. ‘The building’s laid out like a wheel, with spokes leading off the main hub. I usually use the lift, which is right in the centre.’ He stops to catch his breath. ‘Lifts are great, aren’t they?’

‘Come on.’ Kat bounds ahead. ‘We don’t know how long we’ll have before someone catches us.’

We climb to floor three as quickly and quietly as we can, passing nobody and not hearing any signs of life. The door creaks as Kat pushes it open, and we come out of the stairs into a wide, bright corridor with high white ceilings, and glass-fronted offices along each side. A lot of the 67 glass is cracked or shattered and the whole place stinks of smoke.

‘Lucky it’s Sunday,’ I say. ‘There’s no way we’d be able to get through without being seen if there were people here.’

‘If we follow the corridor, we should end up at the hub. I’ll be able to find Mum’s office from there,’ Karim says, breaking into a jog. I guess with everything that’s happened, he’s starting to stress.

It’s only when we reach the central hub that I can appreciate the massive scale of the building. ‘Woah,’ I say, my voice bouncing around the huge space. We’re standing on a balcony that runs in a circle, with the spokes of corridors running off all the way around. A glass barrier stands between us and a long drop to the marble floor below. It’s circular – maybe twenty metres across. Our faces are level with the top of the tallest Christmas tree I’ve ever seen – taller than the one in the town centre even. Most of its baubles are smashed on the floor below, but the tree is upright and in one piece. Above us is a glass roof, cracks splintering across it like a spider’s web, and through it I can see the metal and glass masts on top of the building stretching upwards.

68 ‘This way.’ Karim turns left along the balcony and then left again into a corridor.

Kat gives me a look, and I know she’s as worried as I am about what we’re going to find. We turn into the corridor to see Karim disappearing into one of the offices. He shout-swears and there’s a thud that sounds like he’s booted something. We skid into the room and almost plough into him. He’s standing, breathing heavily, his face in his hands.