Tally Palmer is a successful international photographer, and a celebrity in her own right. When she abruptly breaks off a relationship with Simon Emmet, no one - except Simon himself - is very surprised. But Simon is devastated - and becomes increasingly obsessed with Tally. He blames someone called 'Jack', a mysterious figure from Tally's past.Simon's parents are so concerned about their son that they ask for help from their old friends Alec and Naomi. As Simon's precarious mental state deteriorates, they are drawn into a volatile situation more complex - and dangerous - than they could ever have expected...