An early serial from the long-running BBC television series starring William Hartnell as the original Doctor Who. When the Doctor and his fellow travellers on the TARDIS board a moving spaceship they are surprised to discover that its occupants appear to be dead. Ian Chesterton (William Russell) finally manages to revive a few of the crew and discovers that they have been banned from leaving the orbit of the nearest planet, Sense-Sphere. A number of Sensorites, the race that inhabits the planet, subsequently arrive on the ship and threaten the Doctor and his comrades in a similar manner. A battle of wits ensues in which the humans, aided by the Doctor, attempt to escape the clutches of their alien captors.

The last episode from the first season of this long-running BBC series. While trying to return to 1960s London the Doctor (the first incarnation played by William Hartnell), Ian (William Russell), Barbara (Jacqueline Hill) and Susan (Carol Ann Ford) discover themselves in eighteenth century France caught up in the revolution. They are arrested as traitors and Barbara and Susan are sentenced to death. The Doctor takes on the disguise of a leading revolutionary and must outwit his enemies to become reunited with his companions and save Barbara and Susan.