“Who needs the john?” he asked. Jason said very quietly that he did. Nick unlocked the end of his chain from the handrail above and led him to the bucket at the other end. Jason could hardly walk; his legs were flabby and weak. Nick almost had to carry him.

Nick stood over Jason as he went to the toilet. Sam didn’t think he could go with someone watching him, and was determined to hold it as long as he could.

Afterward Nick slopped some food from the basin into four plastic bowls. It was porridge. Made with salt and water. Sam put his to the side to eat later.

“Best eat it now, kiddo,” Nick commanded. “I need the bowls back.”

Sam reluctantly did as he was told, shoveling the gloopy porridge into his dry mouth. When they finished eating, Nick passed around a bottle of water for them to drink and cleaned out some of the dirty straw where one of the twins had had an accident in the night.

Sam plucked up the courage to speak. “Why are you keeping us prisoner?”

“Prisoner? We’re not keeping you prisoner, kiddo,” Nick said, not unkindly.

“Then why are we chained up in here?”

“For your own safety. Don’t want you wandering off out there and getting lost. Or caught by no nasties.”

“You’re lying.”

“Listen,” said Nick, ruffling Sam’s hair, “we just want you to get fit and well and eat properly, then we’ll see about what we’re going to do with you. Now don’t go worrying yourself. You need to rest.”

He tidied the carriage, tested all the chains, and went out before closing the door behind him and wedging it fast. There were candles still burning on the platform, but inside the car it was dark. Sam sat there miserably, trying to keep bleak thoughts from his mind. Once again he heard the thing on the roof. Shuffling, scraping, sliding.

“What’s that noise?” he said.

“Rats, probably,” said Rhiannon. “Or the cat looking for rats.”

“Do rats ever get in here?”

“No. Nothing gets in here except Nick and Rachel.”

The shuffling noise seemed to shift to the side of the roof.

“I don’t think it’s rats,” said Sam.

“Forget it,” said Rhiannon. “You hear all sorts of things down here.”

Sam stared at the side window for a long time. His eyesight was swimming with blurry dots that weaved themselves into random shapes and broke apart.

He blinked and saw a face at the window staring back at him.

It was floating there, seemingly without a neck or body.

Sam wasn’t sure if it was even human. It was filthy. Covered in dirt. With a bald, pointy crown and a wild straggly beard sprouting from its chin. In the center of its face were two wide eyes, the whites showing around the pupils.

Sam realized with horror that it had no mouth or nose.