The traps, slung over Alex’s skinny shoulder, swung in front of Bea’s face. They had printed diagrams and white writing on the sides that could have been Portuguese.

‘Are these legal?’ asked Bea.

‘Pass me up the rest of the gear when I’m in,’ said Alex.

He banged the trapdoor with his fist. Dust fell as it popped up, releasing the faint smell of rotting flesh. Dan and Bea exchanged helpless glances and climbed up after him.

Once inside it was impossible to imagine the rooms below. The smell was liquid and familiar, as if the smell of corpses was not new, and had only to be recognised. Bea breathed lightly through her mouth. The roof beams came up steeply, so that it was too low to stand upright, except in the middle of the joists. Alex put down his shovel and the red traps, pulling a bandana from his pocket and tying it round his mouth and nose.

‘I put my foot through over there,’ he said, like a bandit.

Light came up through the hole, and dust, swirling.

‘SHH!’ he whispered. ‘They’re very shy, but they’ll protect their young, so look out.’

Dan tried to find the teenager inside himself who would think this was cool and fun but he couldn’t identify with Alex whose risks were all in his head. There was nothing in the real world to threaten him, so he had to create things. Going up into a loft with a rotting floor looking for snakes wasn’t adventurous, it was dumb. And it was almost completely dark. Outside, night had fallen.

‘Torch?’ he asked.

‘I don’t have one,’ said Alex.

‘You don’t have one?’

‘Shit, and I should have brought a bin bag up.’

‘I’ll get it,’ said Dan. ‘And I’ll get my phone. We can use the torch on that.’ He went back down quickly, leaving Alex and Bea alone.

‘There are three or four traps up here already,’ whispered Alex.

‘What’s that smell?’

‘Dead mouse.’

She was aware of the gap between her parted legs as she balanced on the joists, the air moving her skirt slightly. She could hardly make him out in the gloom.

‘If you get rid of the rats,’ said Alex, ‘then the snakes don’t bother coming up.’

‘You said mice.’

‘It’s a fucking zoo, Bea.’

‘How do they get in?’

‘The snakes? They come up through the vines. They can get through tiny, tiny holes, anywhere.’

She thought of her open windows, and the vines growing thickly around the frame.

‘What do we need the bin bags for?’

‘Dead things. Other shit. Whatever.’

Something was poking up from behind one of the joists, shining faintly, wavy edged, like a fin.

‘What’s that?’ she asked. ‘There.’

‘Wait for Dan with the torch.’

Bea took a step closer, balancing carefully. Her brother’s hand reached out. It was bony, and her own was strong and steady. She felt as if she were holding him, not the other way round.

‘Stick?’ she said.