The Earth colony Terra Alpha, the future. With the aid of her sweet-natured executioner, Helen A, ruler of the planet, has ensured the population is happy - on pain of death! The Doctor and Ace decide to fight for the right to be miserable.

Annie Hulley, David John Pope, Georgina Hale, Harold Innocent, Philip Neve, Rachel Bell, Richard D Sharp, Ronald Fraser, Ryan Freedman, Sheila Hancock, Tim Scott