Chappel goes undercover in a prison for sex offenders in order to flush out the ringleaders of a prostitution racket, which involves both the inmates and the prison staff. Reports suggest that inmates are being threatened with violence unless they allow the ringleaders to have group sex with their wives and girlfriends. However, it turns out to be a far more sinister conspiracy. Robinson, unhappy with the situation, tries to get Chappel out, but being so close to collecting the vital evidence, Chappel decides to stay undercover. Posing as Chappel's girlfriend, Hutchins is targeted, while Chappel's behaviour becomes increasingly erratic.