In a story that blurs the line between stage life and real life, celebrated stage star Anthony 'Tony' John Ronald Colman is offered the lead in a new production of William Shakespeare's Othello by theatrical producer Philip Loeb Max Lasker, who hopes Tony's ex-wife Brita Signe Hasso will co-star as Desdemona. Tony initially declines, to the relief of director Ray Collins Victor Donlan, who knows Tony’s mood swells whenever he sinks into a drama. Brita agrees, and warns press agent Edmond O'Brien Bill Friend that Tony shines in comedy but can become terrifying in tragedy, because his immersion in a part can feel like it spills into his everyday life.
Tony changes his mind after growing obsessed with the idea of portraying Othello. While wrestling with the role, he meets waitress Pat Kroll Shelley Winters, and the two begin a casual affair. Brita reluctantly accepts the Desdemona role and rehearsals begin. The production opens to rave reviews, yet Tony’s fixation on jealousy deepens, making it hard for him to separate what is on the stage from what happens off it. He sees jealousy as the engine that will drive his performance and, unknowingly, his fate.
Brita reveals a locket Tony has seen, a gift Bill gave her for her birthday, which sparks a fresh round of jealousy in him. That night, during Othello’s climactic “kiss of death” scene with Desdemona, Tony is consumed by the part and nearly chokes Brita to death. When the show enters its second year, Tony asks Brita to remarry him, but she refuses. He grows restless, suspecting that Brita is involved with Bill, and his suspicion feeds a dangerous delirium. He visits Pat’s apartment, and the lines between stagecraft and real life blur further as he kills Pat with the same gesture that marks the tragedy in the play.
Back at the theater, Al Cooley [Millard Mitchell] stokes front-page publicity for the tragedy by drawing parallels between Pat’s murder and Othello’s famous moment, inflaming Tony with anger toward Bill. Bill grows wary and suspects Tony may be Pat’s killer, reporting his concern to the police, only to learn that Pat’s drunken neighbor has been arrested. Bill contemplates a break, yet his feelings for Brita complicate every decision. Brita finally confesses that Tony left her home the night Pat was killed, deepening Bill’s resolve to uncover the truth.
Bill hires an actress to dress as Pat and plant her as a waitress in the same restaurant Pat once worked in. He invites Tony to the dining room, and with police captain Pete Bonner [Joe Sawyer] watching, Tony becomes distraught upon seeing Pat’s double and bolts from the scene. Suspicion shifts as Bill and the police trail Tony to the theater. Standing in the wings, they witness the tense convergence of performance and reality as Tony, overwhelmed by guilt, continues the improvised tragedy with his life.
In the final moments of the performance, Tony’s guilt reaches a fatal point: he stabs himself with a real dagger at the spot where Othello does in the play. Backstage, bleeding, he confesses everything and dies, leaving the people around him to reckon with the dangerous pull of art when it starts to imitate life.
