Where the stairs turned at the top they opened out into a large, square space with bare brick walls, exposed pipework and piles of discarded junk. A second, iron, staircase led on up to the next level. This part of the museum was nowhere near as grand as the public areas. It reminded Blue of the loft in his mum’s flat. Where she’d piled everything out of the way.

His heart was pounding, but whether that was from climbing the long flight of stairs or from his nerves he didn’t know. He paused to get his breath and let the rest of the group catch up. It was stupid, after all he’d been through, the horrors he’d had to face, to be this scared of a boy. But from what everyone had told him he needed to be scared. The guy had flipped out. Was running around cutting people up. Blue didn’t want to finish this looking like Achilleus, his face rearranged, or Brooke … He hated to think what she was like under that bandage.

Stop it, man. Stop trying to freak yourself out.

Christ, there were six of them! Six against one. That had to be good odds.

Maxie came and stood next to him. She’d stopped making jokes. Her eyes moved constantly, looking for any clues, her sword still down at her side, hand gripping it tightly. She grunted and put her other hand to her mouth. The smell was overpowering here. Something had definitely died.

‘What do you think?’ Blue asked. ‘Could it be him?’

‘What?’ said Maxie, talking in a whisper, although if anyone was up there they’d have heard them all stomping up the stairs like a herd of elephants.

‘Paul,’ he said. ‘Do you think that smell could be him? Maybe he died. Maybe that’s what Fish-Face meant when she said he’d gone away.’

‘Let’s hope,’ said Maxie. ‘I’m not looking forward to having to deal with him.’

‘You’ve seen him in action, Maxie. How bad is he?’

‘Bad …’

Maxie stopped. They’d all heard it. Something moving. It wasn’t loud, just a distant rattle and a thump, but the effect was as if someone had suddenly thrown a switch and passed an electric current through the group.

One of the museum kids swore and they all looked at each other for reassurance.

Blue took a deep breath.

‘Come on.’