In Season 3, Sgt Danny Waldron and his armed-response unit shoot a criminal dead, claiming they acted in self defence. To find out more, DC Kate Fleming is sent undercover into the team.
Loyalties are divided when Steve Arnott comes under scrutiny from his colleagues, and with his career in jeopardy he turns to an unlikely source for help. However, his conduct doesn't go unnoticed by Cottan, who decides to take matters into his own hands. Kate obtains new evidence that means AC-12 are able to question former vice chief Fairbank, but despite her best efforts, she is left frustrated, and Ted Hastings comes under pressure from legal advisor Gill Biggeloe, bringing him to a dramatic decision.
The third series of Jed Mercurio's police procedural began with a big twist when Daniel Mays' bad guy was killed off at the end of episode one. After four equally gripping episodes which delved further into the corruption scandal hinted at in series one and two - and reintroduced Keeley Hawes as anti-hero Lindsay Denton - it seems the feature-length finale promises to up the ante as one of the AC-12 officers finds themselves on the other side of the interview table on suspicion of murder. AC-12 legal counsel Gill Biggeloe puts pressure on Supt Ted Hastings, only for new evidence to turn the inquiry on its head. An undercover investigation may provide the key - but will the unit ever uncover the truth about `the Caddy'? Martin Compston, Vicky McClure, Adrian Dunbar and Polly Walker star. Last in the series.