Spectrum officer Captain Black attacks an alien city on Mars, invoking the wrath of its ethereal inhabitants: The Mysterons. Their first act of vengeance is the attempted assassination of the World President. As part of their scheme, The Mysterons kill Captain Scarlet. They reconstruct him, now invincible and under their control but otherwise indistinguishable from the real Captain Scarlet. Will Spectrum detect the imposter in time? Will fate free the un-killable Scarlet from the Mysteron influence, making him a powerful asset for humanity in this "war of nerves"?

When the Lunar Controller claims he can negotiate peace between the moon and the Mysterons, Captain Scarlet, Captain Blue and Lieutenant Green are sent to the moon to investigate.

The Mysterons threaten to kill Colonel White and after their initial attempt fails, White elects to leave Cloudbase so as not to place the other Spectrum agents in jeopardy.

Captain Scarlet, Captain Blue and Lieutenant Green volunteer for a dangerous mission to remove the power source of the Mysteron complex inside Crater 101, on the far side of the Moon, before it is destroyed by a low yield atomic device.

The Mysterons second target is the Director General of the United Asian Republic. Spectrum swings into action to protect him as he prepares to board his private plane at London Airport.

The Mysterons threaten to destroy London and a truck carrying an atomic device goes missing and is hidden somewhere in the city. The only clue to its whereabouts is the truck driver, found unconscious in the street.

When the Mysterons threaten to destroy key links in the Frost Line Outer Space Defence System, Captain Scarlet and Lieutenant Green race to investigate the mysterious deaths of the personnel at Red Deer Base.

As the Mysterons threaten to destroy the "Heart of New York", Captain Scarlet and Captain Blue investigate the theft of Grade A Security documents from the Spectrum security vaults.

Captain Black engineers the death of chief test pilot Major Gravener, who is retrometabolised as a Mysteron agent as part of the Mysterons' plan to destroy the World Capital, Futura City.

Mysteron agent Judith Chapman, steals a phial of deadly K14 virus - enough to kill ten million people - from Biological Research Station with the intent of poisoning a unknown cities water supply.

Tritonium alloy mining operations at Hotspot Tower in the North Pole are threatened when a Mysteron agent cuts the power to vital heating elements.

When the Mysterons threaten to destroy President Roberts within twelve hours, Captain Scarlet is assigned to guard the skeptical President of the United States.

A manhunt begins for former Spectrum agent Captain Black after a failed break in at a nuclear power plant, where he is accidentally exposed to radiation and becomes detectable for 48 hours.

The Mysterons threaten to obliterate the continent of North America, but Spectrum is left without its number one agent when Captain Scarlet is dismissed for gambling offenses.

Using the Mysteron pulsator recovered from the complex in Crater 101, Dr Kurnitz has developed a transmission device with which Colonel White attempts to contact the Mysterons and sue for peace.

When the Mysterons threaten to sabotage a vital conference at Lake Toma in Switzerland, Scarlet and Blue are assigned to escort the world's leading astrophysicist, Dr. Conrad, to Geneva.

The Mysterons threaten to destroy the Triumvirate of Europe, the three most powerful men on Earth after the World President.

After the Mysterons threaten Spectrum's Cloudbase headquarters, a large fast-moving trace appears on the radar.

The Mysterons' cryptic threat to "kill time" has the Spectrum personnel stumped until Captain Magenta realizes that their target is General Tiempo, the Commander of Western Region World Defence.

Captain Scarlet and the rest of Spectrum are in a desperate race against time to defeat the Mysteron's latest threat, the total destruction of the massive desalination plant at Najama, high in the Andes Mountains.

Spectrum personnel inexplicably take leave of their senses, due to drinking some champagne drugged by the Mysterons, who have threaten to destroy the World Navy Complex at Atlantica.

Following the latest Mysteron threat, Captain Scarlet is dispatched to supervise security at the International Air Conference at Glen Garry Castle in Scotland.

The Mysterons take control of an experimental super-tank in an attempt to assassinate the Supreme Commander of earths armed forces.

When the Mysterons threaten to kill one of the Angels, Captain Scarlet and Captain Blue are sent to Paris, where Destiny Angel is on holiday, to escort her back to the safety of Cloudbase.

Captain Scarlet and Captain Blue are sent to observe an operation to obtain vital orbital reconnaissance photographs of Mars. But the project is put in danger when one of the astronomers is taken over by The Mysterons.