"Bank robbers Kruger, Doig and Carl break into the Spectrum Security Vaults but are disappointed to find only classified information of no material value. Nevertheless, Kruger is fascinated by documents describing Earth's war with the Mysterons, and devises a plan to exploit it.
Meanwhile, the Mysterons inform Spectrum that they have studied human greed and corruption and that they now intend to destroy the "heart of New York". As the city's population is evacuated and its perimeter roadblocked, Captains Scarlet and Blue search the deserted streets for concealed explosive devices.
Driving through forest, Kruger, Doig and Carl stop at a fire tower and feign drunkenness in front of the lookout. They then destroy their car by sending it over a cliff edge, leading the lookout to believe that they have been killed in a drink-driving accident. Returning to the tower, they tell the lookout that they are Mysteron reconstructions and intend to destroy the Second National Bank of New York. When the lookout's story reaches Cloudbase, Colonel White decides that he will not risk lives to protect the bank and orders all Spectrum personnel to retreat to the roadblocks.
Having acquired another car, Kruger, Doig and Carl drive up to a roadblock manned by Captains Magenta and Ochre. They present false FBI identification and claim to be on official business that has nothing to do with the Second National Bank. Ochre's Mysteron Detector shows them to be human and Magenta permits them to enter the city. The men arrive at the bank aiming to steal the entire East Coast gold reserve. However, they have been followed by Captain Black, who locks them inside a vault and warns them that the bank will soon be destroyed.
Learning of the men's arrival, Scarlet is puzzled how a group of supposed government agents knew that the Mysterons were specifically targeting the bank when only Spectrum personnel had been informed. Realising that they are the men who confronted the fire lookout, and that they evidently faked their deaths and are now about to get away with robbery, Scarlet and Blue speed to the bank in their Spectrum Patrol Car but turn around when they see Black driving the men's car in the opposite direction. As the Mysterons use their powers to teleport Black to safety, the bank is destroyed in an explosion. Later, White refuses to accept that Kruger, Doig and Carl were the typical greedy and corrupt humans denounced by the Mysterons and insists that the good of humanity will eventually prevail over the Martian evil."