Parts 1-3 (ITV, 7-8/4/1991)
In a central London bedsit, DCI John Shefford arrives to inspect the body of a young woman who has been brutally murdered. She is identified as prostitute Della Mornay. The pathologist informs Shefford and DC Otley that she was discovered with her hands tied behind her back, having incurred wounds of up to six inches in depth.
Samples indicate that the murderer has a rare blood group, and the finger of suspicion is hastily directed towards George Marlow, a travelling salesman with a previous conviction for attempted rape.
Marlow is questioned at the police station, where he admits to having picked up the victim for sex, but denies murdering her. His common-law wife, Moyra Henson, claims he returned home at 10:30 that night. While in a meeting with Det Supt Michael Kernan, Shefford suffers a fatal heart attack. DCI Jane Tennison is chosen to replace him, despite opposition to her appointment amongst the murder squad. She informs them that the victim has been misidentified - her fingerprints do not match those of Della Mornay.
Following up leads, Tennison identifies the victim as Karen Howard, who had become estranged from her boyfriend after a quarrel. Marlow is released without charge, much to the consternation of Otley who is convinced there is enough evidence to prosecute.
Tennison appears on TV programme Crime Night appealing for witnesses. A woman calls in claiming to have seen a man calling out to Karen Howard, but fails to pick Marlow out of an identity parade. Tennison decides to look into unsolved murders in the North coinciding with Marlow's business trips. She travels to Oldham to investigate the murder of prostitute Jeannie Sharp, only to discover she had had a relationship with Shefford. Two other murders committed while Marlow was in the vicinity come to light.
Frustrated by her lack of progress, Kernan informs Tennison that she is being taken off the case and replaced by DCI Hicock . The decision is later reversed when the squad offer Tennison their 100 per cent backing. Marlow and Henson go on the run, taking separate routes through London. Marlow picks up a set of keys from a King's Cross café and walks to a lock-up garage. He is arrested as he opens the door. Inside, Tennison finds the suspect's allegedly stolen Rover, as well as various torture instruments.
Back at the police station, Tennison confronts Henson with information indicating she knew both Della Mornay and Karen Howard. Henson confesses that Marlow did return at 10:30, but went out again 15 minutes later. Marlow finally cracks, confessing to all six murders. Later in court, he pleads not-guilty to the charges.
