A small group of British sailors stationed on a Scottish island engaged in top-secret research on a new and dangerous torpedo are joined by a US Navy scientist, Lt. Brad Bradville (Gene Kelly), and his assistants. When several tests of the weapon fail, and men are killed, tensions within the group mount. Bradville must prove that the torpedo can work and win over the British, especially Lt. Rogert Wharton (John Justin), before the Admiralty pulls the plug on the project.