After a misunderstanding on the planet Mars, a war is started between humans and an alien race called The Mysterons. Thier first act of revenge is to try and assassinate The World President.
The Mysterons second target is the Director General of the United Asian Republic. The Director is on a visit to London and is scheduled to fly back to Asia via London airport but the Mysterons have other plans.
A manhunt begins for former spectrum officer Captain Black after a failed break in at a nuclear power plant, when he is accidentally exposed to radiation.
When the Mysterons threaten to destroy key links in the Frost Line Outer Space Defence System, Scarlet and Green investigate the mysterious deaths of the personnel at Red Deer Base.
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.
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.
Spectrum leaders and the World President attend a secret conference to demonstrate two new anti-Mysteron gadgets, but the Mysterons announce they intend to sabotage the event.
As the Mysterons threaten to destroy the "Heart of New York", Scarlet and Blue investigate the theft of Grade A Security documents from the Spectrum security vaults.
When the Lunar Controller announces the Moon's independence from Earth in the war of nerves with the Mysterons, Scarlet, Blue and Green journey to Lunarville 7 to investigate reports of an unauthorised complex under construction in the Humboldt Sea.