The British trawler Caistor has disappeared in the Barents Sea. Martin Taylor, son of the Chief Engineer, waits for news in the ship's home port. After the official search is abandoned, a private expedition to Norway is being organised by Tom Silvers, brother of one of the crew, but both British and Soviet Intelligence are determined to suppress public anxiety. As the official inquiry is announced, a lifebuoy is found by a Norwegian fisherman...