Whilst sightseeing in Paris, 1979, the Doctor and Romana notice a series of unexplained temporal disturbances. When a visit to the Louvre lands them in hot water, they realise that a certain Count Scarlioni knows more about advanced technology than a 20th Century Parisian should. With British detective Duggan in tow, the time travellers become embroiled in an audacious plot to steal the Mona Lisa and sell it on the open market. Not only that, but...