In Hackney, detectives investigate a spate of stabbings and encounter one victim who is reluctant to tell them anything. Detectives from the Met's Sexual Offences Unit try to gather evidence against a man suspected of sexually assaulting a woman with Down's syndrome, but with rape being one of the hardest crimes to investigate, they struggle to understand exactly what happened. The Met's dedicated robbery unit, the Flying Squad, use all their undercover surveillance skills in order to catch masked gunmen who have been targeting newsagents and supermarkets in south east London.