The Doctor and his friends find themselves in the lost city of Atlantis, where the crazed Professor Zaroff has convinced the people of Atlantis that he can raise their sunken city from beneath the sea. However, the Doctor discovers a terrible secret behind Zaroff's plan — a secret that could destroy all life on Earth.

• BBC Studios
• Patrick Troughton
• Frazer Hines
• Anneke Wills
• Michael Craze
• Joseph Fürst
• Colin Jeavons
• Noel Johnson
• Tom Watson