Six months after the events of In the Woods, Detective Cassie Maddox is still recovering, Transferred out of Dublin's Murder squad at her own request, she vows never to return. That is, until her boyfriend, Detective Sam O'Neill, calls her one beautiful spring morning, urgently asking her to come to a murder scene in the small town of Glenskehy.
It isn't until Cassie sees the body that she understands Sam's insistence. The dead girl is Cassie's double, and she carries ID identifying her as Alexandra Madison, an alias Cassie herself used years ago when she worked undercover. The question becomes not only who killed this girl, but who was this girl.
Frank Mackey, Cassie's former undercover boss, sees the opportunity of a lifetime, Having played Lexie Madison once before, Cassie is in the perfect position to take her place. The police will tell the media and Lexie's four housemates that the stab wound wasn't fatal. And Cassie will go on living Lexie's life until the killer is lured out to finish off the job.
It's a brilliant idea, until Cassie finds herself more emotionally involved in Lexie's life than she anticipated. Sharing the charming ramshackle old Whitethorn House with Lexie's strange, tight-knit group of university friends, Cassie is slowly seduced by the victim's way of life, by the thought of working on a murder investigation again, and by the mystery of the victim herself.
As Cassie nears the truth about what happened to Lexie Madison and who she really was, the lines between professional and personal, work and play, reality and fantasy become desperately tangled, and Cassie moves closer to losing herself forever.