A fictional story, though inspired by real events, "Hidden Agenda" has an agenda of its own to make the rest of the world aware of the British government's cover-ups and illegal tactics in Northern Ireland, in particular the sanctioning of "shoot to kill" policies that allow officials to kill suspected terrorists.
Specifically the film is based on the covered-up affairs involving Harold Wilson, Colin Wallace and John Stalker. Combining those stories and showing them through the eyes of a pair of Americans (Frances McDormand, Brad Dourif, who played abusive husband and abused wife in "Mississippi Burning") who are doing investigations for the International League for Civil Liberties, screenwriter Jim Allen and director Ken Loach have taken a documentary-style, gritty approach that is at times uncomfortably realistic.
Most of the film has to do with McDormand's character looking for answers to a pair of shooting deaths two men in a car. The local police claim the car was driving right at them and they fired to protect themselves. They also claim that the two men were armed and dangerous.
Yet, the facts surrounding the incident don't add up to the policemen's statements and with McDormand's help, a conscientious police investigator from London (Brian Cox) is determined to uncover the truth.
Along with the film's low-key, realistic approach, the performances by all the players but especially the leads are excellent, with McDormand and Cox getting more and more frustrated with each brick wall they encounter.
The film is a bit slow and at times slightly strained, and there are moments when you'll be hard-pressed to understand all the dialogue but on the whole it is effective and chilling.