A comet is coming and nobody knows what that means, so Moomin just walks toward the mountains to find out. The journey matters more than the destination, the characters you meet more than the apocalypse you're running from. By the time you reach the Observatory, you've forgotten to be afraid of the end of the world.

Strange things have started happening in Moominvalley, and the Muskrat warns that a comet is on course to strike the valley and wipe everything out. Moomin, Sniff and Mee set out for the Observatory in the Lonely Mountains to learn whether his warning is true. On their journey they meet Snufkin, the Hemulen and the Snorks, and they go through a string of adventures. The 1992 film is a fantasy adventure with comedy, adapted from Tove Jansson's Moomin book of the same name.