Ruth Lennox, beloved mother of three, is found by her daughter in a pool of her own blood. Psychotherapist Frieda Klein finds she has an unusually personal connection with DCI Karlsson's latest case. When her niece befriends Ruth Lennox's son, Ted, she finds herself in an awkward position. When it emerges that Ruth was leading a secret life, her family closes ranks and Karlsson finds he needs Frieda's help more than ever before. But Frieda is distracted. Having survived an attack on her life, she finds herself chasing down a path that seems to lead to a serial killer who has long escaped detection. Or is it merely a symptom of her own increasingly fragile mind?