The Protectors investigate an insurance fraud involving an old friend of Harry's who, having previously staged his own death, is killed for real.

A strange space cloud hides an alien invasion fleet with a plan to conquer the Earth - starting with Space City!

The Stingray crew brave the perils of a newly discovered underground sea.

An alien crystal causes Lieutenant Andy Conroy, Straker and other SHADO operatives to hallucinate.

An Eagle and its crew are crushed to death by an enormous energy field in space. When one of Alpha's astronauts is possessed by the anomaly, he tells them the energy field is a living space brain, which responded to the 'threat' with antibodies. Finding the Moon on a collision course with the Brain, the Alphans make plans to avoid the same fate as the Eagle.

Joe intervenes when it seems that there is more to Mac's new girlfriend than meets the eye.

After Alan Tracy returns to motor-racing, his rivals decide to remove the competition by rigging a bridge with a movement-sensitive bomb, which will explode the moment that Alan and Grandma Tracy try to escape.

Masterspy kidnaps Dr. Beaker and demands Supercar as ransom.

When the Fireball XL5 crew finds the wreck of a spaceship that disappeared decades before, their search for the lost pilot, Col. Denton, leads them to the planet Arctan – where they discover Denton living quite happily as king of the Ice People.

While Christmas preparations are underway at both Tracy Island and a local children's hospital, which is expanding to incorporate a new radiotherapy wing, a pair of criminals attempt to burgle a high-tech vault storing gold bullion.