Captain Richard Decatur (Edmund Lowe) is a young commander who is an undercover agent for the U.S. secret service. His ship cruises in the Panama Canal zone where he uncovers an enemy plot to dynamite the famous passage that connects the Atlantic and Pacific Oceans. Peg Williams (Martha Mansfield) is the sultry vamp who tries to pry information out of the Captain. Knowing she is in league with the villain, he plays along to learn more about the nefarious scheme. Richard is drummed out of the service only to be reinstated as a hero for his bravery. Alma Tell plays Richard's faithful wife, with Betty Jewel as the Latin-beauty Delores. This patriotic film did much to spark interest in the U.S. Navy and is the first English language film for the legendary Bela Lugosi.