Top nuclear scientists around the world have been mysteriously disappearing. When aircraft engineer Steve Rossi (George Raft) vanishes at the airport shortly after landing in London, Scotland Yard are alerted. In fact Rossi has disappeared intentionally. He's an undercover FBI agent assigned to track down the brains behind an international kidnapping ring - a ring responsible for smuggling scientists behind the Iron Curtain. Rossi's British counterpart is MI5 agent Joan Miller (Sally Gray). But is she really who she claims to be?