Melancholia is a science fiction drama that focuses on a young woman named Justine, her sister Claire and Claire's husband John. Justine has recently gotten married, and the film begins at her wedding reception. However, despite the happy occasion, Justine is depressed and grows more morose as the evening wears on. Later that night, Justine's new husband decides he's had enough and leaves her.
The next day, Justine goes out with Claire. She notices that a bright red star she'd seen in the sky yesterday has disappeared. Later, John tells Justine and Claire that the star has disappeared because a planet, called Melancholia, has passed in front of it. He tells the women that he's excited because the planet is supposed to pass close by the earth, and they will be able to see it. However, instead of being excited, Claire begins to believe that Melancholia is going to crash into the earth. The news has little effect on Justine, who is so depressed she almost can't get out of bed. As Melancholia draws closer, though, it becomes clear that Justine is the only one calm enough to deal with what may soon happen.