Billy is a loner. His older brother bullies him, and his good timing mother passes him off to a succession of one night uncles. At the age of 15 years, he is on the brink of an aimless existence of petty pilfering and wasted weeks of schooling, which he realises only too well will lead to some dreary dead end job. Wandering in the woodlands near his Yorkshire village, he finds a young kestrel hawk and becomes intrigued with the bird's grace, its power and freedom. He steals a book on falconry and proceeds with a quiet dedication to train the bird, which he calls Kes.

The bird is Billy's avenue to freedom and a brief vision of another kind of life.