Before the film, Moomintroll's father had finished building Moominhouse. During one rainy evening, the Muskrat suddenly appears at the front door to stay because his riverbank home had been destroyed by Moominpappa's bridge, built earlier that day. The next day, the rain's turned everything black and according to Muskrat, it is soot from outer space. He believes that a threat is coming from space and nothing can be done. Moominpappa gets an idea about the astronomical observatory in the Lonely Mountains, where a telescope can see far into space. The next morning, on their way, the trio meets Snufkin for the first time. He's heard about a comet which could crash to earth at any time, and joins the group. After that, they climb the steep mountains towards the observatory, while Moomin finds a golden anklet. Snufkin knows that the anklet belongs to the Snorkmaiden.