The Valet leads Joseph Garcin into the Second Empire drawing room. Garcin discovers there are no mirrors, no windows, no beds, and no way to close his eyes. He begins to comprehend the nature of his damnation.

Ines Serrano is brought in. She immediately mistakes Garcin for her torturer, then recognizes the real arrangement: they are meant to torture each other. She refuses all pretense and begins dissecting Garcin's self-presentation.

Estelle Rigault arrives and insists there has been a mistake. She attempts to maintain her social facade, but the absence of mirrors forces her to depend on others for confirmation of her own existence. The three-person dynamic locks into place.

The three characters gain glimpses of the living world they have left behind. As their connections to life fade, they are forced to confront their sins fully. Each character's self-deception is systematically dismantled by the others.

The characters attempt various pairings and strategies to escape their mutual torment. Garcin and Estelle try physical intimacy; Ines disrupts it. Ines appeals to Estelle; Estelle recoils. Every alliance collapses because the excluded third party cannot bear to watch.

The door suddenly opens. No one leaves. Garcin refuses to go until Ines validates him. She refuses. The door closes. Garcin delivers the play's verdict: 'Hell is other people.' The eternal torment is confirmed.