Major Thorpe (writer and artist), Mort Leav (pencils and inks)
Published in Jumbo Comics #53, Jul 1943 - 8 pagesA French spy has stolen the plans for a new mine detector from the Germans. He is hunted in the sewers of Paris but manages to float them away. They are discovered by a young woman outside of town who goes to a lot of trouble to make sure the name on the package, ZX-5, gets them.
Here are the pages I have of it.