Constance Worth

Nazi spies in America attempt to rob the formula of synthetic oil and ship it to Germany by means of a night plane called the Dawn Express.

When Professor Carroll, a U.S. Army scientist, is murdered after formulating a powerful chemical explosive, Military Intelligence assumes the criminal investigation, leading to a foreign spy ring. Carroll's younger brother, Army Corporal Greg (Eric Linden) goes AWOL with a goal of locating his sibling's killer. Greg is known to have had in his possession a list of other researchers involved in the development of the explosive who are in danger. Both M.I. and a number of enemy agents are after him to obtain the list.

When an assistant DA becomes the accidental hero of a police capture, crooked leaders try to exploit him in a plot to cover up their own crime ring.