New Year, or a clock with a cuckoo. Children"s detective with fantasy elements

Once upon a time, during the time that there are no references in any textbook, a person lived side by side with magical creatures. Magic was then common and helped a lot, because the equipment was not yet invented. As time went. People, first very dependent on wizards, gradually learned to live without their help and refused patronage. Fortunately, the fact that people began to do without magic does not mean that all other creatures that inhabit our planet abandoned it. On earth and today, magicians, gnomes, elves live among us.
Larry and Roberta are ordinary Christmas elves, and their everyday life never differed from the everyday life of the thousands familiar to all of us by boys and girls. The oddities begin on one of the boring winter days. The grandmother first behaves very mysteriously, and then completely disappears. An old clock disappears from the wall in her bedroom, and the domestic ghost carries a complete nonsense about some unknown where and when a crack that appears, threatening the catastrophe of our entire planet. I propose to conduct an investigation and find out who the grandmother Larry and Roberta turned out to be, where a crack appeared and what kind of disaster threatens the earth. Well, are you ready?