In the Scottish Highlands, an elderly lady named Mrs. Mackenzie is alarmed to see green lights hovering over the nearby Grampian Nuclear Power Station; she reports the incident to the authorities, but no one believes her. When Colonel White learns of the incident he immediately sends Captain Scarlet and Harmony Angel to investigate. But that turns out to be just what the Mysterons want as the Spectrum Rhino ground vehicle is just what they need to breach the reactor's defenses.

Joe is assigned to rescue a fellow WIN agent from an impregnable stronghold before his captors force him to divulge classified information.

A nuclear bomb must be discretely removed from the Arctic wastes of the Eastern Sector to avert a world war.

When Bossy Boots discovers Pom-Pom has returned home to Mr. Bumbledrop, she insists that he returns her ragdoll, Flopsy. Torchy offers to take her to Topsy Turvy Land to retrieve the doll, but she refuses, so Mr. Bumbledrop decides to use reverse psychology to get her into the rocket. Once she arrives in the strange land, she's horrified to discover she's shrunk to the same size as Flopsy, who begins exacting her revenge.

Brogan and Haldane discover a capsule containing the body of a Tarn male. The autopsy reveals that the Tarn is missing vital organs, removed with surgical precision, and Brogan and Haldane find themselves on the trail of organ leggers from Danae – vicious killers who murder for profit and target Brogan as their next donor!

With the townspeople unhappy with Tex's dealing of a spate of robberies by a gang of thieves, Tex turns in his badge and joins the thieves as a crook.

The aliens are preoccupied with the birth of Cy-star's child while the Terrahawks prepare to launch a sneak attack.

When the Mysterons seemingly threaten the President of the United States with assassination, Spectrum implements maximum security measures around his residence. But as the Mysterons' self-imposed deadline approaches, Scarlet realises that the organisation is protecting the wrong target.

A radio call from planet Earth to the Moon gives hope of transporting the Alphans back home, until things go terribly wrong during the first crewed transport sequence.

Troy, Phones and Atlanta are sent to Scotland to solve the mystery of Nessie once and for all.