|Peter Lorre||Professor Karl Fenninger|
|Boris Karloff||Judge Spencer Mainwaring|
|Bela Lugosi||Prince Saliano|
|Helen Parrish||Janis Bellacrest|
|Alma Kruger||Aunt Margo Bellacrest|
|Dennis O'Keefe||Chuck Deems|
Janis Bellacrest books Kay Kyser and his big band to play at her 21st birthday party. Between performances, Kyser has a series of disturbing interactions with Bellacrest's bizarre guests, including quirky Aunt Margo, pretentious professor Fenniger, creepy Prince Soliano and irritable Judge Mainwaring . When a powerful storm blows in, Kyser and Bellacrest begin to suspect something treacherous is afoot.