Major Thorpe (writer and artist), Mort Leav (pencils and inks)
Published in Jumbo Comics #37, Mar 1942 - 8 pagesAt home working a deciphering a message, ZX-5 is visited by an aunt he never knew he had. She proceeds to try and drug him and when that does not work, her associates show up. This is all to learn what he knows about a fifth column plan to blow up a factory.
Here are the pages I have of it.