Disgraced detective Zain Nadir is interviewed about drug trafficking in Hayesend Prison, where he is serving ten years for perverting the course of justice, after Callum and Will discover the body of a drug addict recently released from prison. He agrees to help his colleagues infiltrate the gang involved. Jack is not sure whether he can trust his mole and fears the worst when a riot breaks out just as the police move in to arrest the operation's kingpin, Zain's cellmate Jason Forbes, who makes good his escape in the confusion.