After seeing four planets explode in a dead galaxy, Flash and crew get word that Earth is next. An alien race, somewhat reminiscent of Nazi's has planted planet busting bomb to destroy Terra. The alien will die at noon with the Earthlings, but is happy to do so to see Earthlings vaporized. Flash Gordon is dispatched to go back to 1955 Berlin to save Earth. Planet fall is made at Washing D.C., then New York. The radiation source is traced to Europe and the ship crosses the ocean in five minutes. The ordinance they see is a planet-busting, slow-acting nuclear bomb was hidden in Berlin some thousand years earlier by using a stolen time machine.
Flash and crew are chased by German police, but get away. Scenes of post war Berlin show old bomb damage. The bomb is located with minutes to spare. It is disarmed with two seconds to spare.