The dam where Thumbelina and her father live is breaking due to the rising waters in the nearby pond. Father worries that when spring comes, the melting snows will rise the water higher than ever causing the dam to crack and water to flow over the meadow, thus drowning the little people who live there. Father believes he is too old to take on the journey to find the prince and warn him and his people, so he asks his daughter to go instead. Thumbelina agrees, but in her journey she mets a great deal of characters, both good and evil. To someone not bigger than a human's thumb, dealing with the evil intentions of Mona, a greedy mouse, will prove to be a big challenge.