The setting is Hillsboro, a small rural Tennessee town, during the summer of an unknown year. Bert Cates, a sophomore science teacher, has been arrested and jailed for violating the Butler Law, which prohibits the teaching of evolutionary theory in public schools. Rachel Brown, a fellow teacher and his girlfriend, pleads with him to apologize and admit that he was wrong. Cates, however, refuses to give up.
The townspeople are excited because Matthew Harrison Brady, three-time presidential candidate, famous orator, and fundamentalist leader, is arriving in Hillsboro to join the district attorney, Tom Davenport, in prosecuting Cates. The atmosphere of the town is similar to that of a country fair. Banners are flying and people are selling lemonade, hot dogs, and Bibles. The Ladies' Aid has prepared a picnic for Brady and his wife, Sarah, and everyone is in a festive mood. During the celebration, Brady discovers that Rachel Brown, the daughter of the spiritual leader of Hillsboro, Reverend Jeremiah Brown, is a friend of Cates. He tricks her into revealing confidential, incriminating conversations she and Cates have had.
At the picnic, E.K. Hornbeck, a cynical columnist from the Baltimore Herald, reveals to Brady and the townspeople that famous defense attorney Henry Drummond will be Cates' attorney. This news shocks everyone, and Reverend Brown compares Drummond to the devil. Later that evening, Drummond arrives in Hillsboro alone.
