"Captain Black breaks into the Culver Atomic Centre but is discovered by security guards. While making his escape he is forced to enter a radioactive area, where he is exposed to an isotope that renders him detectable on long-range Geiger counters for the next 48 hours. In a bid to capture the Mysteron agent, Spectrum search the surrounding area using a fleet of Detector Trucks aided by the Angel fighter squadron.
Trapped inside the search area, Black murders a filling station mechanic to steal the hidden Spectrum Pursuit Vehicle that he is guarding. When Captains Scarlet and Blue arrive to requisition the SPV, they encounter the Mysteron reconstruction of the mechanic, who pulls a gun on them but is shot dead by Scarlet. The Detector Trucks pick up Black's trace as he speeds down a highway in the SPV. Captain Ochre sets up a roadblock to stop him. However, the Mysterons warn Black and order him to return to the atomic centre, where the background radiation will make him undetectable to Spectrum. Sighting the SPV from the air, Symphony Angel lands her fighter. She is captured by Black, who uses the SPV to crash the atomic centre's gates and takes Symphony deep into the complex.
The Spectrum forces converge on the atomic centre. Black attempts to kill Symphony by exposing her to increasing levels of radiation, but ultimately chooses to spare her life. He instead forces the Angel, who is now radioactive herself, to drive out of the complex alone in the SPV. Thinking that Black is the driver, the Spectrum forces begin a pursuit. The entrance to the complex is left unguarded, and Black decontaminates himself and slips away. Symphony crashes the SPV and Spectrum discover too late that they have been tricked. After Colonel White's debriefing, Lieutenant Green discreetly asks Symphony why she did not alert the Captains of her presence during Black's escape; she admits that she had never driven an SPV before and did not want to bypass such an opportunity."