The Mutants

The Time-Lords send the Doctor and Jo on a mission to deliver a sealed message pod to an unknown party on board the Skybase orbiting Solos in the 30th century. Solos hopes to gain independence from Earth, but the Marshal is determined to stop this from happening.

The Marshal has the Earth administrator killed, and a Solonnian named Ky is blamed. Ky flees to Solos with Jo as a hostage. The Doctor follows them to Solos and meets them inside a thaesium mine. Ky is the intended recipient of the Time Lord pod, and it opens for him, revealing stone tablets with carved inscriptions.

They meet up with an Earth scientist who was investigating the mutating disease that affects the Solonnians. He has found that the thaesium radiation is in fact part of the natural life cycle. The Doctor returns with a crystal back to the Skybase, where he is captured by the Marshal, and forced to work on a machine that will destroy Solos's atmosphere.

The Marshal is killed when Ky first transforms into a mutant, and then into an ethereal being, which is the final stage in the life cycle.

• Marshal: Paul Whitsun-Jones;
• Ky: Garrick Hagon;
• Cotton: Rick James;
• Stubbs: Christopher Coll (1-5);
• Varan: James Mellor (1-4);
• Varan's Son: Jonathan Sherwood (1-2);
• Administrator: Geoffrey Palmer (1);
• Jaeger: George Pravda (2-6);
• Sondergaard: John Hollis (3-6);
• Old Man: Sidney Johnson (3);
• Solos Guards: Roy Pearce (4), Damon Saunders (5);
• Guard Warrior: David Arlen (4);
• Mutt: John Scott Martin (5);
• Investigator: Peter Howell (6);


• UNCREDITED CAST:
• Old Man: David J. Graham;
• Guard Warrior: Ian Elliott;
• Earth Control Guards: (all 6) Gary Dean, Barry Hooper, Keith Urry, Mick Urry;
• Advisors: Ken Nazarin, Evan Ross;
• Mutts: Laurie Goode, Bill Gosling, Nick Thompson Hill, Mike Mungarvan, Rick Newby, Eddie Sommer, Mike Torres;
• Skybase Guards: Keith Ashley, Ali Baba, Dave Carter, Ronald Gough, Atley Harvey, Dennis Plenty, Ron Tingley, Terry Walsh, David Waterman;
• Solonians: Reg Cranfield, Brychan Powell, Vic Taylor, Peter Whitaker;
• Guard Leaders: Damon Sanders, Martin Taylor;
• Warriors: Derek Chafer, Alex Hood, Steven Ismay, Terry Sartain, Terry Walsh;