Robbie Coltrane stars as Fitz, a brilliant but flawed, wise-cracking criminal psychologist who looks behind the evidence of murder to discover what lies within the criminal mind. Fitz takes some teaching work at the University, where he begins receiving love letters. Janice, a lab technician, is the writer of the letters and in her depression begins murdering male students lured into her room. The police want to take Fitz off the case as they understand that the murderer is writing to, and killing, for him. Janice changes tack and lures Fitz's son to her flat, but when the police catch her, she is alone. With Mark Fitzgerald's life in jeopardy, Fitz must use all his powers of interrogation in finding his son before it's too late.