Morgiana

Morgiana (1972) is a mystery, horror, drama directed by Juraj Herz rated 7.2/10.

Jealous of her vapidly "good" sister's popularity, poisonous Viktoria doses pretty Klara's tea with a slow-acting fatal substance. As the latter grows hysterically weak, the former finds success increasingly compromised by guilt, blackmail, and the pesky need to kill others lest she be exposed.