The film follows the adventures of three mouse chirdren: a mischief-maker named Johnny, a lazy pants named Jacder and their young sister named Sarha. One day, the three children sneak off to go fishing only to stumble across the home of a cautious, intelligent and overweight kid named Chuck and his cousin, Flynn. Reasoning that climate change will cause the death of many animals within the next century, Chuck has developed a potion that turns animals into fish so they can survive the rising sea level and also an antidote to reverse the process. Unbeknownst to all, Sarha drinks the potion, gains a fish tail, and gets tossed out of the potal into the sea by Chuck. Since Johnny and Jacder saw Sarha's transformation, they head out onto the ocean in a desperate search. When a storm blows in, Jo