Another adventure for the seventh incarnation of the philanthropic Time Lord. The Doctor (Sylvester McCoy) and Ace arrive on the planet Segonax, home of the Psychic Circus. Ruled over by the evil Chief Clown and his gang of robots, the Circus is designed to entertain a masked audience of three - and failure meets with instant death. Joined by the boastful Captain Cook and his companion, Mags, the Doctor and Ace enter the Circus talent contest - and find themselves having to compete with killer bus conductors and werewolves along the way!

In 1714 Parliament offer a £20,000 prize for anyone who can provide an accurate means of measuring longitude at sea. John Harrison (Michael Gambon) flies in the face of popular opinion by saying that the stars do not provide the answer, and provides his own solution with the invention of a mechanical clock. However, it takes Harrison forty years to prove his theory, and he is eventually forgotten in the mists of time. Centuries later, Robert Gould (Jeremy Irons) attempts to restore Harrison's reputation by tracking down and repairing the four clocks he originally constructed.