‘The weight of the snow must have caved that bit of the roof in,’ Ethan said, squinting upwards. ‘Pretty weak roof to start off with. Guess they didn’t have time for roof repair before shoving him in here.’

‘What are we going to do?’

They stared at Moses. He pulled the squelching bed sheets up under his nose and stared back at them, his wide eyes moving from one to the other. God knows what his brain thinks we are right now, Thea thought.

‘We can’t leave him in here,’ Ethan decided. ‘It’s cold, for one thing.’

‘I don’t know …’

‘I get it – he’s dangerous. I’m not stupid. But I can handle it. We’ve just got to move him to the kitchen, put him in the chair, handcuff one arm to the radiator. I’ve had to take him to the toilet enough times. He knows the drill.’

Thea eyed Moses warily. Moses was definitely awake more often and, though quiet, Thea often saw him watching them. She remembered the Moses in the video diary, the happy-go-lucky, joking one from the start … the clever one. Clever enough to make the technology. Clever enough to outsmart her and Ethan.

Thea sighed.

Around the lighthouse that night, a new, cushioned, white world formed in the quiet dark hours that saw Thea awake, Moses shackled to the radiator and Ethan cuffed to his bed.

It was the morning of their third day in the lighthouse. They sat on the floor, drinking tea and eating crackers.

‘We can’t stay here much longer,’ Ethan said, while dipping a cracker into mayo. They were running out of food now too. All that was left was a pot of jam, the crackers and mayo, some tins of beans and the dregs from a box of cereal.

‘I know.’

Thea rolled her shoulder experimentally. It hurt.

‘I had a date not so long ago.’ Ethan snapped a cracker. ‘Before we started the trial. Met her on the web, hooked up for a drink. Thought it would be awful, because dates generally are. It wasn’t.’

He tapped the lid of the jam and paused.

‘Didn’t think I might not see her again.’

Thea’s cracker snapped in half, one end mired in mayo. A lot of sensitive, compassionate comments could have been made at this point.

‘It’s probably best you only got one date.’ She smiled. ‘No time for you to screw it up.’

Ethan puffed out a breath of air like he’d been punched. ‘Harsh!’

But it had worked: he smiled and rubbed his hand over his bristly hair.

She munched a dry cracker, which coated the roof of her mouth.

‘What about you?’ He leant forward, his arms over his knees. Thea noticed his forearms. They were tanned and strong-looking, then she blushed for paying attention to something like that when they were stuck here. In the lighthouse at the end of the world.