An Edwardian yacht in deep space races around the planets. There is a double agent in the TARDIS crew. The White Guardian warns the Fifth Doctor of great danger. Turlough must finally choose sides and at the end of the race lies the prize of Enlightenment.
| Directing | Fiona Cumming | Director |
| Writing | Barbara Clegg | Writer |
| Production | John Nathan-Turner | Producer |
| Writing | Eric Saward | Script Editor |
| Sound | Malcolm Clarke | Original Music Composer |
