Dayton Raslor, owner by inheritance of a successful spaceship corporation, is imprisoned in a penal colony on Jupiter for a crime he didn't commit. He had been framed by three ruthless industrialists on Earth who are plotting to take over his Spaceline. Raslor manages to escape from Jupiter with the aid of the son and daughter of his company's financial director, who had been driven to suicide after also being framed by the same industrialists. The trio plot their revenge by forming "The Black Avengers" and as interplanetary outlaws attack the spaceships of the stolen corporation...