A top-secret meeting is held with the World President and two Spectrum Intelligence Agency officers to showcase the new Mysteron electrical gun and detector. Following the inexplicable events with the late Doctor Magnus, who attempted to kill General Tiempo, the meeting takes place in the shooting grounds of an African private game reserve.
Colonel White and Captains Scarlet and Blue find themselves in a treacherous hunting sport when the Mysterons attempt to prevent Spectrum from introducing their new and innovative mobile weapons in the fight against them.
But, unbeknown to the group of men the security officer-in-charge, Captain Indigo, has been murdered in cold-blood by Captain Black and is now threatening the lives of everyone at the meeting. Can Scarlet stop him in time and save everyone?