‘They’re great!’ said Kate. ‘I think we’ve done really well.’

‘Right,’ said Lana. ‘But would you like to climb this one on your zip wire, out over the tentacles?’

Kate looked at the pieces of knotted plastic. She scrunched up her nose, but didn’t immediately say no.

‘How about we plait them together?’ I asked.

‘But that’ll mean we’ve got far less rope,’ said James.

‘Yes, but what we’ve got will be stronger.’

‘But what we’ve got here would probably be long enough to reach the boat already,’ said James. The boat had moved towards the shore a little, but with a good rugby kick we’d still be able to reach it. And combined together, the four plastic-bag ropes we had between us were easily long enough to reach beyond the tentacles.

‘I think . . .’ I said, looking over at the activity surrounding the Big House, ‘I think we should make it strong and not worry about reaching the boat for now.’

‘What are you thinking, Mystery Martha?’ said James.

Kate started plaiting three of the ropes together.

‘I’m not sure,’ I said. ‘But I know we’ve made loads of escape attempts before. I don’t even know how many. We’ve never tried something with rope though. We can tie things up now, and lasso things and maybe pull things towards us. That’s new.’

‘And us,’ said Kate.

‘Us what?’

‘Well, us coming up with the escape plan. That’s also new.’

Dr Jones dropped a large pile of plastic bags next to us. Most were shredded, or discoloured by time spent floating in the sea. ‘There are more on the way,’ she said. ‘Not all are as good as these, though. And it might take a few minutes.’