Count Karnstein sends for a doctor to help his sick daughter Laura. Her nurse believes she is possessed by the spirit of a dead ancestor, Carmilla. A young woman becomes intrigued by the mysterious deaths surrounding Laura after a carriage accident outside the castle forces her to stay. They become close friends until Laura becomes convinced the spirit of Carmilla is forcing her to kill.
| Actor | Role |
|---|---|
 Christopher LeeCount Ludwig Karnstein | Count Ludwig Karnstein |
 Adriana AmbesiLaura Karnstein | Laura Karnstein |
| UUrsula DavisLjuba | Ljuba |
 José CamposFriedrich Klauss | Friedrich Klauss |
 Véra ValmontAnnette | Annette |
 Carla CalòLjuba's Mother (as Cicely Clayton) | Ljuba's Mother (as Cicely Clayton) |
 José VillasanteCedric | Cedric |
 John KarlsenFranz Karnstein (uncredited) | Franz Karnstein (uncredited) |
 Ignazio BalsamoNot listed | Not listed |
| AAngel MidlinNot listed | Not listed |
| NNela ConjiuNot listed | Not listed |