The one-act play opens on a drawing room with Second-Empire style furniture and a massive bronze statue on a mantelpiece. A quiet yet mysterious looking Valet leads Garcin, a journalist from Rio, into the room. Garcin is at first very confused as to what is going on. He claims that he does not like Second Empire style furniture, asking if all the rooms are like this one. The Valet is evasive but Garcin then admits that he actually had a habit of living with furniture he didn't like. Garcin then exclaims that this is not what he expected hell to be like. The Valet laughs at Garcin for wanting his toothbrush and asking where the bed is: he has not fully accepted his death.
Garcin pretends to be at ease but is frightened by the Valet not having any eyelids. It bothers him to have someone stare at him so intently. He begins to worry about having to keep his own eyes open during eternal daylight, especially when there are no books around, but the Valet calmly reminds him that he is dead. As he leaves, the Valet points out a bell that should summon him, but he says that it does not always work. Left alone, Garcin gazes at the bronze statue for a moment, but then repeatedly rings the bell and tries to open the door. As soon as he gives up and sits down, the door opens.
The Valet brings in a women named Inez, who had been a postal clerk in Paris. She immediately thinks that Garcin is a torturer, but he laughs at her, wondering how she could confuse him for one of the staff. She coldly replies that she knows how torturers look, having often watched herself in mirrors. Garcin realizes that there are no mirrors in the room. She also explains that she doesn't like men. Despite her coldness, Garcin tries to make peace with Inez, explaining that they must be courteous to each other in order to make the best out of their situation. She replies that she is not polite and then yells at him for twisting his mouth. She tells him that there is no need to be frightened since they are already dead, but Garcin thinks they have not yet begun to suffer.
The Valet reenters followed by Estelle, a wealthy young housewife from Paris. She thinks that Garcin is someone else but won't say whom. Inez instantly takes a liking to her, offering to switch couches with her and wishing that she had flowers to give her. Estelle just died of pneumonia and seemingly watches her funeral from the room, remarking that no one is crying. Inez asks her if she suffered and she says no, that she was only half conscious. The same holds true for the other two: Inez suffocated in her sleep from a leaky gas stove and Garcin was shot by a firing squad.
Estelle asks them not use the word "dead," but the word "absent" instead. Garcin begins thinking about his wife, who does not yet know he is dead. He exclaims that she got on his nerves. The two women ask him not to take his jacket off even though it is stiflingly hot in the room and he obeys. After this incident they begin to wonder why they have been placed together. Estelle thinks that it is all absurd and that they should be with friends and family instead. Garcin agrees, saying that their being together is a fluke. But Inez disagrees, explaining that nothing has been left to chance. She thinks the room was set with them in mind.
Existentialism is primarily a reaction against the traditional philosophical approach to objective and abstract understandings of human behavior. Instead, existentialists choose to study individual human beings who exist independently of cultures, traditions, and laws. The setting of No Exit is thus the perfect existentialist "laboratory" to study three separate individuals who are divorced from the world and people they knew. Left in an empty room/cell their actions and feelings will thus define exactly who they really are. The lack of mirrors amplifies this situation. Each person is given a choice: will they define who they are on their own or rely on the other inmates to decide who they are?