Six-year-old boy Mitya decided to give his mother an unusual gift for her birthday, namely to bake her a cake. While looking for a cake recipe in his mother's cookbook, he finds a drawing with mysterious people and learns from his grandmother that these are gummy people - residents of the Sweet Planet. Mitya goes to the Sweet Planet to meet its inhabitants and find out what cakes are made from. Once on the planet, he meets the marmalade men Marnie and Ladna, who agree to help him find the necessary ingredients for the cake. Mitya, traveling around the Sweet Planet, learns a lot of interesting things, helps the inhabitants of the planet and purchases the necessary products for the cake.