The Secret Code (1942) is a 15-chapter Columbia Pictures film serial directed by Spencer Gordon Bennet. It is an action-packed wartime espionage thriller centered on Nazi sabotage during World War II.

The story follows Police Lieutenant Dan Barton (played by Paul Kelly), who fakes his dismissal from the force to infiltrate a Nazi spy ring. Under the masked identity of The Black Commando, he works undercover to stop enemy agents from disrupting key American war efforts. His mission is complicated by the presence of Jean Ashley (Anne Nagel) and Detective Sergeant Pat Flanagan (Clancy Cooper), as well as numerous Nazi spies working within the country.

A unique aspect of The Secret Code is its educational component—each chapter features a brief lesson on cryptography, teaching audiences about secret codes and how they can be used or broken.

The serial, released during wartime, was patriotic propaganda designed to raise public awareness about espionage threats while delivering high-energy action and suspense.