American salesman Jack Robinson falls in love with Englishwoman Cynthia Marley and they visit her family so he can ask for permission to marry her. She points out to him that her relatives are rather eccentric and, by the way, a cousin has just died. The remaining members of the clan are; the sinister Reginal; Percival, an inventor who has recently discovered electricity, the phonograph, and several other handy items; Natalia, a macabre, vampire-like creature; Cornwallis, a hammy and dapper ex-actor; Grandfather, who lies bedridden upstairs; and, by the way, Muldoon, who is kept locked up in the fear that he will harm someone. Several attempts are made on his life which leads Jack to believe that the Marleys are a shade past eccentric.