Bad Seed

S3 E2: A husband and wife are brutally murdered in their beds. Another woman is killed as she lies sleeping in the middle of the afternoon. A prostitute is discovered dead in the local canal. Worryingly for Tony, the killings bear the same MO as those of newly-released killer Mack 'the Knife' McMurray, who claims to have been reformed and educated during his long years in jail and has now enrolled as a PhD pupil in Tony's class. Investigations reveal a tangled web of personal relationships between the victims but none of it makes sense. Tony is tormented by the notion that Mack is the murderer, a notion strengthened by Mack's sardonic needling and his apparent need to supplant Tony in the public eye. Meanwhile Carol has her own problems: her biological clock isn't so much ticking as ringing, and she needs to find someone to father a child. Her personal crisis causes friction with Tony - is she inviting him in or shutting him out? It dawns on Tony that the killer shares some of Carol's obsession with fertility. But the death of somebody close to Tony and Mack's renaissance as media pundit about the crimes spurs Tony into a moral crisis. Can he and Carol achieve the self-knowledge required to solve this crime?