Harry is disturbed to be called to a crime scene at the home of a family he knows, and finds the bodies of the mother and her teenage daughter, while her stepson lies in a coma - although her toddler has been left unharmed. The police suspect the woman's husband to be the killer - but the pathologist is not so sure of his guilt. The double-murder investigation reveals more about the tangled lives of the inhabitants of Magnolia Drive. Harry makes a significant discovery about the dead woman's stepson Charlie, found lying in a coma at the crime scene, while Leo sets out to recreate the shape of the mystery weapon, with the help of forensic scientist Gill Bailey.