Four further episodes chronicling Captain Scarlet's attempts to save the earth from the threat of Mysteron attack. 'Fire at Rig 15' sees fire expert Jason Smith taken over by the Mysterons and his talents bent to their own destructive ends. 'Treble Cross' finds the Mysterons falling victim to their own rotten tricks when they monkey with Major Gravener. 'Flight 104' has Captains Scarlet and Blue serve as bodyguards to a leading astrophysicist. And 'Place of Angels' sees the Mysterons endanger the entire population of Los Angeles when they get hold of an ultra-deadly virus and threaten to drop it into the water supply.