Mrs. Emma Peel and John Steed are spies who work for the secret branch of the British government called The Ministry. They are called in to investigate Prospero, a plot to blackmail Britain by controlling the weather. Emma Peel is suspected of being involved but it is discovered that she has a double who works for the real baddie, Sir August de Wynter. He threatens to freeze Britain, at one point unleashing a blizzard on Trafalgar Square.