A comet is speeding towards Earth and nobody knows what to do!

Will it destroy everything and everyone? Moomintroll decides to find out. So, with Sniff, he sets out on an expedition to ask the Professor if a comet is really on its way to destroy the Earth. On their journey they meet some interesting people - such as Snufkin the super tramp, and the Hemulen who rescuesthem from an underground tunnel - and have narrow escapes from such menaces as crocodiles and giant lizards. And on their way back Moomintroll meets the beautiful Snork Maiden and is a changed Moomin for ever after. But what about the comet - and is the World Wiped Out?...