Captain America Comics #43

Cap and Bucky discover a Nazi plot to obtain Zorite, a new metal that makes plane and tanks more fuel efficient. When two geologists are found dead, a \"shadow monster\" is blamed for the murders. The Nazis are setting up a local painter who is painting shadows in the act of committing murder to be the fall guy so that no one will realize the Nazis are stealing the Zorite vein. Cap chases the truck with the metal and hits the driver in the face. Rather than be sent to death as a spy, the driver heads off the cliff attempting to kill both Cap and himself, but Cap leaps free of the truck.