When Chappel finds a young girl prostituting in Soho, he attempts to uncover her identity, learning that she absconded from a children's home in Sheffield. Paying a visit, he discovers all is not as it seems, that young girls are being lured away, with the promise of gifts and a life of luxury, in order to work the streets of London.

A huge web of lies and deceit covering up a dangerous child abuse ring is discovered to be limited not only to those now living in the children's home but to past residents as well. Chappel suspects the involvement of one of the staff members, and encounters a terrifying chain of events.

Tasked with investigating an illegal gambling and prostitution ring operating out of a pub, Chappel and Hutchins posing as thrillseekers. However, after Chappel nearly blows his cover, he's shocked to discover that the haunt is frequented by former Vice officer Dougie Raymond.

Chappel begins to use Raymond's connections as a means of gathering evidence, but when Dougie's level of enthusiasm – and hope that his efforts may win him his job back – backfire, Chappel's reliance is left in tatters.

When the team raid a brothel operating as a massage parlour, they discover that the young female employees have been smuggled into the country from Eastern European refugee camps. One girl offers to testify against the ringleader, but only if she is given round-the-clock protection.

Chappel assigns Joe Robinson to the case, unaware that the girl is actually harbouring feelings for Robinson. When his wife Shirley becomes suspicious of his interactions with the girl, Robinson finds his marriage on the rocks and the impending pressures of the job becoming too much. Chappel is forced to find new evidence after the girl reveals that she's pregnant and no longer willing to testify.

Robinson and Hutchins are on a stakeout, watching a violent pimp suspected of attacking one of his girls. When the pimp confronts him, Robinson, still wound-up from the last case, as well as the impending collapse of his marriage, attacks the john in front of several onlookers. When the pimp is found murdered the next day, the blame is soon directed to Robinson's door, with evidence of his run-in from the day before.

With Robinson's increasing aggression and temperament, it seems to paint him the prime suspect. However, Chappel believes otherwise and sets out to find the real killer.