Maggie stared down at the forest canopy below. TAKE THE PLUNGE! read the sign in front of her. Strapped into a harness, holding tight to a cable, she was standing at the top of a zip-slide, having impetuously picked this as the bravest and most un-Maggie-ish thing she could do today. But now her stomach was saying, Don’t do this and her head was saying, You could die and . . . Actually this was a ridiculous idea. What had she been thinking? She didn’t need to throw herself off a tiny timber platform 150 feet high to prove anything to anyone, she—

‘You’re not scared, are you?’ said the man, who looked a lot like Helena, now that she peered at him more closely. Wait, that was weird. What was she doing here? ‘Okay, I’m taking your silence to mean you want a push,’ said Helena. ‘Ready . . .’

‘No!’ yelped Maggie, because she hated the thought of being pushed.

‘Steady . . . GO!’

‘WAAAARRRGGHHHHH!’ Maggie screamed as she was shoved off the platform.

Then she sat bolt upright in bed, panting. Sweat broke out on her forehead. It was just a dream, she told herself shakily. Just a dream.

She blinked a few times and the morning swung into focus. Oh yeah. Now she remembered. Today was the first day of the rest of her life. So what was she going to do?

A few miles away, Olivia was clambering down a wooded slope. She was making her way tentatively, legs trembling with the exertion, when she skidded on some loose stones and had to clutch at a sapling to stop herself plunging all the way down. As she clung to the tree, her heart pounded, but she kept her balance and let out a shaky breath. This was not how she usually spent her Wednesday mornings. Then again, this was not a usual kind of day.

She had woken up following the luxury of another full night’s sleep. Her fourth day in Cornwall and already she felt like a different person from the frazzled, crying woman who’d driven, shouting aloud, down the motorway. The white noise had quietened to a faint hiss of static in her head, but family life in Bristol still felt distant, as if it belonged to somebody else.

How are you? When will you be home? We all love and miss you so much, Mack kept texting, with accompanying photos and little videos of the boys. Any time she dared turn her phone on there would be another flood of new messages. But looking at them and the pictures was like gazing at another person’s life. What did it mean, the complete lack of compulsion she felt about returning – her blank feelings of nothingness? Was she a monster? Or just malfunctioning?