Josh and his two friends look for the person who stole a peregrine falcon from its nest.

As she grows through the first years of her life in the Catskill Mountains of New York, a peregrine falcon called Frightful interacts with various humans, including the boy who raised her, a falconer who rescues her, and several unscrupulous poachers, as well as with many animals that are part of the area's ecological balance.

Deep in the mountain forest, a hungry weasel stalks a nest of baby peregrine falcons.