The Doctor is chosen for a quest by The White Guardian to go in search for the six segments to the Key to Time, that have been scattered and sent throughout the time/space continuum. With the Key to Time, The White Guardian will restore balance to the universe. Joined by a young time lady named Romana, The Doctor, Romana and K-9 Mark 2 begin their quest and arrive at their first destination, The medieval Russian like world Ribos, where a conman named Garron bids to sell Ribos to a exiled tyrant known as Graff Vynda K, where Unstoffe, Garron's assistant uncovers Garron's scheme and is unaware he is in possession of the first segment of the Key to Time.