Based on the TV series the film follows DI Regan and DS Carter as they became embroiled in a deadly political scandal. One of the leading members of the government, Charles Baker (Ian Bannen) is about to secure a huge deal with OPEC stabilising the world oil market and boosting Britain's position within it. Baker is the rising star of government, regarded a future prime minister, who is closely controlled by his urbane, manipulative American press secretary Elliot McQueen (Barry Foster). When Regan investigates the mysterious death of a prostitute as a favour to one of his informants, he becomes aware that Baker and McQueen might be involved. A spate of killings follow - which sees Regan take on both the criminals and the hierarchy of the Metropolitan Police and British security services.