A Nazi spy ring is after a chemical formula that increases the power of ordinary gasoline for U.S. Army aviation use. Two U.S. chemical companies are developing the formula, with each working on half for security purposes. The spies get half the formula and know that either of two chemists, Robert Norton (Michael Wilding or Tom Fielding (William Bakewell), knows the rest. They capture Fielding, through a ruse by gang member Linda Pavlo (Constance Worth, and threaten the life of his sister Nancy (Anne Nagel) and his mother if he does not give them the formula. To protect his friend Fielding, who does know the formula and is engaged to Nancy, Tom pretends to know the secret and boards the Dawn Express plane with the spy leader and his gang.