The White Guardian warns the Doctor of a terrible peril, and sends the TARDIS to an Edwardian racing yacht. The Doctor is amazed when he realised that the yacht is, in fact, a space yacht and that the race is around the Solar system! The Captain, Straker, and his officers are Eternals - immortal beings with little imagination, racing for the ultimate prize of Enlightenment. The Buccaneer Captain of another ship, Wrack, is a servant of the Black Guardian and must be prevented from winning the race at all costs!