Line of Duty - Season 3 Episode 1 -

A hardened criminal is shot dead by an armed-response unit led by Sgt Danny Waldron, who claims they were acting in self-defence. But when AC-12 gather evidence suggesting it was a deliberate killing, DC Kate Fleming is sent undercover into Danny's team to find out more. She is quick to identify tensions within the team - only for her own conduct to come under scrutiny.