We might have our suspicions, but we can’t be sure yet that Garcin is in hell. Our initial situation is a guy by himself in a drawing room populated by Second Empire furniture and some rather cryptic props (make sure you see "Symbols, Imagery, and Allegory on that note).
Remember, hell is other people. There’s no conflict for Garcin when he’s alone. The arrival of the two women brings with it a host of problems, among them such existentialist ideas as "the look," competitive subjectivity, objectification, and a lot of bad faith. (We explain all of these concepts in Character Analysis, which you should definitely read.)
We can’t really pin down a specific complication, but the initial conflict – other people – certainly gets messier as the play progresses. Details like the personal histories of the characters, the scenes witnessed back on earth, and the tense interactions between all three individuals serve to raise the emotional involvement of the audience and the emotional stakes of the play.
This monologue right here is the climax of No Exit. Garcin has reached the breaking point and is physically raging again the door keeping him in hell. Notice that he – not Estelle or Inez – is the focus of this emotional climax. (For more evidence that he’s our protagonist, see "Character Role ID").
When the door finally opens, Garcin doesn’t run out like a mad man. Instead he ponders reflectively, "I wonder why that door opened." For a few seconds we’re left with the suspense of the decision facing out main character: stay or go?
The denouement is the stage in which everything is made clear, and in this case, what needs to be cleared up is Garcin’s seemingly inexplicable decision to remain in hell when he was supposedly free to go. His explanation is rather explicit: he needs to remain behind to convince Inez that he’s not a coward. (If you’re interested in the existentialist’s reaction to and judgment of this decision, read Garcin’s "Character Analysis.") What’s most interesting about this part of the play is the consequences it has for the bleak future Garcin and the others face. No longer are they the helpless victims of the management, (the "they), keeping them against their will. Instead, this hell is a chosen hell. Garcin has chosen this "agony of the mind." According to Sartre and his concept of personal freedom, Garcin has to make a choice, and he has to be held responsible for the fall-out. He has no one but himself to blame for hell – and its lack of exits.
All of the arguments, reasoning, debates, and questions in No Exit have led the three main characters – and the audience – toward this indisputable conclusion: hell is other people. That’s why there’s no need for hot pokers or other torture devices. That’s why hell is simply three people in a room together. The characters’ reaction to this conclusion – uncontrollable laughter – is interesting in and of itself, and we talk all about it in "What’s Up With the Ending?" See you there.