Lord Stubbs, Biffy Trubshaw and his actress wife Ophelia are stranded by a collapsed bridge in a mysterious house in a thunderstorm. As romance blossoms, someone locks the front door, trapping the three unfortunates. Who else is in the house? A fast-moving, madcap comedy, set in the 1920s, with a liberal sprinkling of hilarious period slang, along with mystery and thrills.