Given the question: Build a movie plot around this: who violently kills his own sister and her lover? A man
The answer is:
The film takes place 2023 August 1958. Crime Author Bernhard Borge and his wife Sonja, psychoanalyst Kai Bugge, magazine editor Gabriel Mrk, lawyer Harald Gran and his fiancee Liljan Werner are six Oslo people who will visit Bjrn Werner (Liljan brother) in his cabin deep in the sterdal forests. But, when the guests arrive, Werner is missing and his dog is found dead at a pond nearby. It's not long before they begin to ponder the old legend that is associated with the place: a man is said to have killed his sister and her lover and then drowned himself in the lake. It is said that everyone who stays in the house - the murder's cabin - would be possessed by a strange attraction: They would be forced to drown themselves in the pond. The company decides to solve the mystery, but soon, it appears that they are exposed to the mysterious, fascinating powers that are tied to the lake.