The kids' awesome sandcastle gets trampled overnight. A lone set of footprints along the beach leads to a prime suspect who claims not to have seen their sandcastle, yet he's carrying a big shell that once adorned it. As it turns out, no one touched their castle. The culprit was the rising waters of high tide. When the gang discover a set of ski tracks that run on either side of trees, boulders and through fallen logs, Huckle leads Lowly and Sally in a quest to discover who could do such a thing. Ultimately they figure out that the tracks were made by two mice snowboarding side by side on mice size snowboards.