Southern Italy, around 1865-70. Excited villagers mill about as a small theatrical road company arrives at the outskirts of a Calabrian town. Canio, head of the troupe, describes that night's offering, and when someone jokingly suggests that the hunchback Tonio is secretly enamoured of his young wife, Canio warns he will tolerate no flirting with Nedda. As vesper bells call the women to church, the men go to the tavern, leaving Nedda alone. Disturbed by her husband's vehemence and suspicious glances, she envies the freedom of the birds soaring overhead. Tonio appears and indeed tries to make love to her, but she scorns him. Enraged, he grabs her, and she lashes out with a whip, getting rid of him but inspiring an oath of vengeance. Nedda in fact does have a lover — Silvio, who now arrives and persuades her to run away with him at midnight. But Tonio, who has seen them, hurries off to tell Canio. Before long the jealous husband bursts in on the guilty pair. Silvio escapes, and Nedda refuses to identify him, even when threatened with a knife. Beppe, another player, has to restrain Canio, and Tonio advises him to wait until evening to catch Nedda's lover. Alone, Canio sobs that he must play the clown though his heart is breaking.
The villagers, Silvio among them, assemble to see the play Pagliaccio e Colombina. In the absence of her husband, Pagliaccio (played by Canio), Colombina (Nedda) is serenaded by her lover Arlecchino (Beppe), who dismisses her buffoonish servant, Taddeo (Tonio). The sweethearts dine together and plot to poison Pagliaccio, who soon arrives; Arlecchino slips out the window. With pointed malice, Taddeo assures Pagliaccio of his wife's innocence, firing Canio's real-life jealousy. Forgetting the script, he demands that Nedda reveal her lover's name. She tries to continue with the play, the audience applauding the realism of the "acting." Maddened by her defiance, Canio stabs Nedda and then Silvio, who has rushed forward from the crowd to help her. Canio cries out that the comedy is ended.