In a small Michigan town, an army lieutenant is arrested for the murder of a tavern owner who he believes raped his wife. Desperate and without funds, the wife seeks the help of Paul Biegler, a former district attorney who has since turned to small-time lawyering after losing his re-election bid. Despite reservations, Biegler agrees to take the case, drawn by both the challenge it presents and a sense of justice for his clients. He finds himself up against a seasoned prosecutor, brought in from the big city, and the case quickly attracts national attention for its scandalous and morally complex nature.

Biegler employs a meticulous and crafty approach to the defense, delving into the intricate details of the case and exploring every legal avenue available. As the trial progresses, the defense hinges on the notion of "irresistible impulse," a plea suggesting that the lieutenant was mentally uncontrollable at the time of the murder due to the alleged rape of his wife. This defense strategy leads to a series of intense courtroom battles, featuring sharp legal maneuvers and the examination of various witnesses, each adding layers of complexity to the case. The trial uncovers a web of lies, deceit, and hidden motives, challenging the boundaries between law, justice, and morality.