It's the start of a bank holiday weekend and a young man has been stabbed in Hackney. Police constables Dave Carron and Paris Smith rush to the scene but the victim doesn't want to tell them anything about what's happened. As he is taken to hospital the next emergency call comes in - less than a mile away there has been another stabbing. For Dave, one of Hackney's most experienced response officers, it's an all too familiar Friday night but for Paris, arresting anyone for a knife is one of the most satisfying things she can do.

Across London, detectives from the Met's Sexual Offences Unit are trying to gather evidence against a man suspected of sexually assaulting a woman with Down's syndrome. Rape is one of the hardest crimes to investigate and detectives are struggling to understand exactly what happened in her flat that night. If they can't, there will be no chance of bringing her attacker to justice.

Staff in newsagents and supermarkets in south east London have been terrified by masked gunmen demanding that they hand over money. The Met's dedicated robbery unit, the Flying Squad, have been called in. Using all their skills of undercover surveillance and forensics, detectives are in a race against time to catch them before they strike again. Show less