Two sisters find their already strained relationship challenged as a mysterious new planet threatens to collide with Earth. On the day of her wedding, Justine (Kirsten Dunst) struggles to keep her severe depression in check and appear happy in front of all her family and guests. But cracks begin to show under the pressure of adhering to the schedule set by Justine's brother-in-law, who paid for the wedding. Only Justine's sister, Claire (Charlotte Gainsbourg), seems to understand what she is going through and tries to help her finish out the night, but to no avail. As the planet Melancholia bears down on Earth, Justine finds unexpected peace in the thought of imminent destruction, while Claire spirals into terrible anxiety, desperately seeking a way to save her family. The contrast between the sisters' reactions to the impending catastrophe highlights their deep emotional struggles and the different ways they cope with fear and uncertainty.