Sherlock Holmes comes to the aid of his friend Henry Baskerville, who is under a family curse and menaced by a demonic dog that prowls the bogs near his estate and murders people.
Sgt. Cannon (Tommy Cannon) and PC Ball (Bobby Ball) run the police station in the quiet town of Little Botham. When the station is threatened with closure due to a lack of crime, they decide to invent some crimes to justify their existence. When they try to steal a painting from a local rich businessman (Roy Kinnear), they accidently stumble across a gang of real art thieves who have just stolen £1 million worth of paintings. It is up to the two bungling cops to stop them escaping with their haul.
Sontaran Field Major Styre is conducting experiments on the survivors of future Earth in preparation of a full-scale Sontaran invasion of the planet. Can the Doctor defeat Styre and save the world?
