Just outside Earth's atmosphere lies Skybase, a vast floating aircraft carrier that's headquarters to an international security group called the Spectrum Organization, tasked with maintaining peace on Earth.
Mysterious signals lead Spectrum agents Captain Scarlet and Captain Black to Mars, and the dawn of a war of terror with evil invisible aliens, the Mysterons. A war in which both men will play lead rolls — on opposing sides.
Captain Scarlet, free of Mysteron control, but made virtually indestructible by them, begins a desperate search for the aliens' instrument of destruction, Captain Black — and must stop a countdown to the end of the world!
Skybase is invaded by a swarm of deadly robotic bugs, and Lieutenant Green could be all that lies between survival and destruction for the whole of Spectrum.
Captain Scarlet leads a rescue mission when Spectrum loses contact with its base on Mars. But Scarlet, Blue, Destiny, Harmony and Dr Gold find themselves trapped by a deadly intelligence.
Fifteen years after he went missing on the first manned mission to Jupiter, Lieutenant Green's father returns to Earth in a cryogenic sleep — but is it really him?
Captain Blue and Destiny Angel are stranded above the Earth in an orbiting space shuttle controlled by a crook with a plan to blackmail Washington. Things can only get worse when Captain Black intervenes.
The Angels have a close escape when on-board electronic systems fail. Scarlet and Blue find a connection with crop circles appearing in southern England — and the only way to stop Captain Black is a piece of history.
When missile launch codes are stolen from a military base Destiny is identified by security cameras as the thief. Have the Mysterons taken her over? Scarlet must find out.
Captain Scarlet discovers a plot to destroy Skybase. But when Mysteron agents try to kill him, Scarlet wakes up in Skybase sickbay and finds a grieving Destiny Angel — and no-one can see or hear him. Can he save Skybase from beyond the grave?