DI Chappel runs into former boss DS Frank Vickers in a Soho brothel, past secrets are unearthed that threaten to destroy both the vice squad and Chappel's personal life. Investigating the death of a prostitute, Chappel tries to enlist the help of an ex-girlfriend, but she has moved on from the sex trade.

Chappel goes undercover in a prison to flush out the ringleaders of a prostitution racket thought to be pimping young women to inmates. PC Hutchins, posing as Chappel's girlfriend, is targeted by the group.

Chappel resolves to resume his relationship with Jane, now working as an escort, but the corrupt DS Vickers is sniffing around her too.