Film adaptation of a stage play based on the Scopes 'Monkey trial' of 1925. When Tennessee schoolteacher Bertram T. Cates (Dick York) is put on trial for teaching Darwin's theory of evolution, the prosecuting counsel appointed is fundamentalist politician Matthew Harrison Brady (Fredric March). While Brady stirs the town up into a religious fervour against Cates, the liberal Henry Drummond (Spencer Tracy) earns the wrath of the townsfolk by defending the teacher. Cynical journalist E.K. Hornbeck (Gene Kelly) is sent to cover the trial, which takes place in a sweltering courtroom where passions run as high as the temperature.