Frightful’s Mountain is the third novel in a series. It is preceded by My Side of the Mountain and On the Far Side of the Mountain, in both of which Sam is the protagonist. The first two novels revolve around Sam’s mountain home and adventures in the Catskill Mountains with Frightful as his companion. In Frightful’s Mountain, however, Frightful becomes the protagonist, and the novel deals primarily with the life cycle of falcons and their importance in nature. While the first two novels give Sam’s point of view, Frightful’s Mountain focuses on the falcon’s.

In My Side of the Mountain, Sam runs away from his home in New York City to survive independently in the Catskill Mountains. He realizes that survival skills are more difficult to put into practice than he anticipated and finds he has a lot to learn. When he captures a baby falcon, which he names “Frightful,” she becomes his companion and helps him hunt. To communicate with Frightful, Sam studies her body language and various calls. Together, they develop a special bond. Frightful sees Sam as her mother because he raised her and she imprinted on him as a baby bird.