Deborah is a history postgraduate student, living with three flatmates, one of whom is her long-term boyfriend James. The relationship becomes increasingly fractious as Deborah's finals draw near. Her fitful sleep is punctuated by inexplicable bouts of sleepwalking; James seems less than sympathetic. After seeing a psychologist, Deborah realises that the cause of her unease is the fact that James is having an affair. After a blazing row, he storms out and, the following morning, Deborah wakes up next to a blood-spattered claw hammer. What has she done? Could she have attacked someone in her sleep? Is she really going insane? Or has someone taken advantage of her affliction?

• Anthony Horowitz

• Art Malik
• James McAvoy
• Keeley Hawes