June and Cass are called to the flat of a prostitute named Allie after tracing malicious calls made from her phone, only to find her lying unconscious on the floor from a vicious assault. Turning her over reveals the words 'Join The Club' written on her back. The case matches several other recent assaults on prostitutes in the area, most of whom are being pimped by Robert Stern. After being apprehended it is revealed that Stern attacked Allie but was not responsible for the calls she made or the writing on her back. Meanwhile June saves Beth, another of the victims, from throwing herself under a train believing herself to be HIV positive after her attacker revealed this to be the words sinister meaning. When he is eventually caught and brought back to the station, Liz identifies him as ex-boyfriend Andy Marshall, a search of his houseboat turns up HIV medication. The calls were being made to his wife Julia Marshall who is pregnant and living on her own, unaware of his supposed HIV stat

With insufficient forensic evidence to charge him, DI Neil Manson and DS Samantha Nixon have 24 hours to extract a confession from serial rape suspect Alan Kennedy. CPS laywer Jonathan Fox, who previously defended Kennedy on an assault charge, watches the proceedings with great interest, but the stress may be too much for him, and he jeopardises his relationship with Insp. Gina Gold when he makes a comment about her not having children. With police scouring Kennedy's mother's flat for forensic evidence or clues which will help, Manson and Nixon continue their interview, but Kennedy is a tough nut to crack. The next day, literally at the last minute, Nixon puts the pieces together and Kennedy finally confesses. Simultaneously, Dr Hugh Wallis finds a knife in the flat. With Kennedy behind bars, the relief attend a community party organised by Supt. Okaro, but the fun is quickly over when a massive bomb explodes.