Hilja and her little sister Taimi are sure: Santa Claus and the Christmas elves really exist! But Hilja thinks a few pieces of evidence wouldn't hurt. So, during the Advent season, when she's not baking gingerbread, sledding down the stairs, or putting on a rather stubborn nativity play, Hilja is on the lookout for clues about the Christmas magic. However, all she and Taimi discover is that Grandpa reads too many detective novels and that Grandma Johannisbeer secretly snacks on chocolate, even though it's not a candy day. It isn't until the night before Christmas Eve that Hilja finally sees a lot of red pointed hats running around in her living room.