Morgiana (1972)

When their wealthy father dies, his daughters Viktoria and Klára inherit his fortune. The evil Viktoria inherits a small castle and all the possession inside including jewelry but the naive Klára inherits most of his assets. Viktoria plots to poison her sister with an undetectable liquid to inherit her fortune. Klára feels sick and her doctor cannot diagnose her, while Viktoria meets a blackmailer.