After a landing on Mars by a Spectrum exploration vehicle, Earth is under attack from the Mysterons. As Captain Scarlet and the other Spectrum agents prepare to defend the Earth against a terrible threat, they know that anything could happen. For the Mysterons have powers beyond the understanding of man - and they are determined to destroy all life on Earth! Captain Black becomes the Mysterons' pawn, and Captain Scarlet takes on a vital job, escorting the world president on a dangerous journey. But can Scarlet resist the dangerous powers of the Mysterons? An explosive and action-packed adventure based on the first episode of the sensational TV series.