Beiker and Hopkiss are invited to test drive a new atomic train. They discover the train has been sabotaged and Supercar is needed to try and save them using a new tool recently developed for the United States Army.
Dr Beiker along with Jimmy undertake a flight in Beiker's latest project - a balloon. Unfortunately the balloon is accidentally released from its moorings by Mitch and Supercar is launched in a desperate attempt to save them.
Master Spy now rich beyond his wildest dreams decides rather than steal Supercar he will just outright purchase the car. Unfortunately for him, Dr Beiker has decided Supercar can not be purchased for any price.