Wally Brown and Alan Carney are Jerry and Mike, the stars of a weekly radio “unsolved mysteries” series. Ellen (Anne Jeffreys), the show’s head writer, is given invaluable script advice by famed criminologist Marsh (Lionel Atwill). Little do our heroes or heroine realize that Marsh is actually The Cobra, a wily murderer who kills for the thrill of it. When Mike, Jerry and Ellen pay a visit to Marsh’s baronial estate, the villain and his faithful servant Stone (Bela Lugosi) do their best to kill off the troublesome radio sleuths with an abundance of old-dark-house gadgetry. But Mike and Jerry have the last laugh in a tension-filled climax.