1940s mystery thriller-horror based on a play by Bernadine Angus. Leo Grainger (George Zucco), recently released from prison after being falsely framed for embezzlement, now lives on the remote Fog Island with his stepdaughter Gail (Sharon Douglas). Leo was set up by a group of former business associates, and he suspects that one of them was also responsible for killing his wife, Gail's mother. Intent on revenge, Leo invites the group to his island home, luring them with hints about a hidden stash of money. When the guests arrive, the atmosphere of mutual suspicion and the thick fog swirling around the island make for an intense weekend of danger and intrigue for all concerned.