The Moomin family is hibernating when one day they are awakened by Mr. Hemul. He is very busy and tells them that they cannot possibly continue sleeping, because after all, "Christmas" is coming soon. Christmas!? The Moomin family has never heard of it because they always sleep during the cold season. Who or what could it be? And when will it arrive? Could it be dangerous? To be on the safe side, Moominpappa decides to prepare himself and his family for all eventualities.