Inez, Estelle, and Garcin are in hell - that is to say, a Second Empire drawing room with no windows, no mirrors, and a single locked door. Once they come to terms with their situation, they begin to wonder why they have been sent to hell. What crimes did they commit? Garcin argues that he was a pacifist who stood up for his principles, while Estelle explains that all she did was refuse to leave her husband for a lover.
The characters decide to stay quiet and keep to themselves. This attempt at non-interaction does not last for long, however. Inez is attracted to Estelle and repeatedly tries to win the pretty Parisian over. Garcin, annoyed, finally reveals why he is in hell after all: he treated his wife "abominably." He then procures Inez's story: she ran away with her cousin's wife. Estelle is next in line. Inez and Garcin gang up on her and coax out the details of her sordid past: when she became pregnant with her lover's child, she fled to Switzerland with him, gave birth, and drowned the newborn baby. Her lover killed himself as a result.
Estelle, hungry for a man's attention, begs for Garcin's affection - much to Inez's dismay. Tensions come to a boil when Garcin demands that Estelle trust him, and reveals his greatest worry: that he may be a coward. It turns out that his "pacifism" was expressed by his attempt to flee his country instead of courageously facing down his opponents at home. For that crime, he was sentenced to death, and, as he confesses, he faced his demise "miserably...rottenly." Inez now has a leg up and digs deep into Garcin's conscience, tormenting him with the specter of his cowardice.
When the door to the room swings open and Garcin is given the opportunity to escape, however, he chooses to stay, determined to convince Inez that he is not a coward, but Inez refuses to play along. Finally, after Estelle, in a rage, tries to kill Inez (who, of course, is already dead) with a paper knife, Garcin cries out: "Hell is - other people!"