Don't close your eyes. Don't fall asleep. Don't let them in.

Thea is an insomniac; she hasn't slept more than three hours a night for years.

So when an ad for a sleep trial that promises to change her life pops up on her phone, Thea knows this is her last chance at finding any kind of normal life.

Soon Thea's sleeping for longer than she has in a decade, and awakes feeling transformed. So much so that at first she's willing to overlook the oddities of the trial — the lack of any phone signal; the way she can't leave her bedroom without permission; the fact that all her personal possessions are locked away, even her shoes.

But it soon becomes clear that the trial doesn't just want to help Thea sleep. It wants to control her sleep...

An unputdownable, gripping psychological thriller for fans of The One, Behind Her Eyes and Girl A!