In the city of Beaverton, Mabel Tanaka spends her childhood with her grandmother in a nearby forest glade teeming with wild animals. Inspired by her grandmother, Mabel grows up with a deep appreciation for nature and continues watching over the glade after her estranged parents leave town and following her grandmother's death. When Beaverton's mayor, Jerry Generazzo, announces plans to replace the glade with a freeway—claiming that all the animals have left—Mabel campaigns against the project but receives no support. Her activism causes her to neglect her college studies, drawing the disapproval of her biology professor, Dr. Sam Fairfax.