The Maclean brothers, Norman and Paul, grow up in Missoula, Montana with their father, Presbyterian minister John, from whom they learn a love of fly fishing for trout in the Blackfoot River (Montana). They learn to cast using a ticking metronome. The boys become accomplished fishermen as a result. Norman and Paul are home taught and must adhere to the strict moral and educational code of their father. As they grow older, it becomes clear that Norman is more disciplined and studious, while Paul is fun-loving, wild, and the more talented fisherman.