Act III takes place in November, two months after the end of Act II. The votive light under the Virgin gleams even more brightly. Juno and Mary discuss Bentham, who has disappeared to England without leaving Mary his address. Mary was madly in love with her fiance, even though she admits Jerry may have been the better man, and wonders if he left because her family wasn't good enough for him. Juno supposes it was a bad idea to introduce him to Joxer and Mrs. Madigan and laments that Mary waited so long to share the news with her mother.
Juno speaks with Boyle, who complains of pains in his legs. The two argue over the fact that they still haven't received any money, although they are deep in debt. Boyle asks for some stout (a type of beer), liniment, and a newspaper, and Juno places a second bottle of stout on the table. Juno and Mary leave, heading for the doctor as Mary is not feeling well.
Joxer and Nugent enter the room while Boyle is in the bedroom. Nugent tells Joxer how he went to the lawyer's office and found out that Boyle will be getting no money, due to the way the will was written. The lawyer has told the same thing to Boyle, who has visited repeatedly. Nugent complains that Boyle never paid for his suit, and Joxer says he is glad he had nothing to loan him.
The two hear Boyle coughing and realize he is in bed. Nugent opens the door and asks to be paid; rather than acquiescing, Boyle asks for a heavy top-coat as well. Angrily, Nugent rushes into the room and takes the suit, much to Boyle's dismay. At the same time, Joxer slips the bottle of stout from the table and puts it in his pocket.
Boyle complains about Nugent to Joxer, who expresses his outrage and feigns ignorance of the event. Joxer wonders aloud if perhaps Nugent had heard something about Boyle not getting the money. Boyle realizes his second bottle of stout is gone from the table and blames that on Nugent as well.
Mrs. Madigan enters and asks for the three pounds back that she had raised by selling blankets and furniture. Boyle says that isn't possible, and that she'll have to wait. Intent upon getting her money back, Mrs. Madigan takes the gramophone, ready to bring it to the pawn shop, though complains that is hasn't even been paid for yet. After she leaves, Joxer expresses his outrage again, yet again wonders aloud if perhaps she has heard something about Boyle not getting the money. The two argue and Joxer leaves.
Johnny and Juno enter; Juno is visibly upset. She sits the family down and explains that Mary is pregnant. Boyle threatens to go to England to find Bentham and bring him back to marry her, then complains about what Mary's plight will do to him and his reputation. Juno points out that Mary will have far more to deal with. Boyle wants to tell his daughter off, but Juno says that if he does, she and Mary will both leave. Johnny has little sympathy either and wants to drive his sister out of the house. Juno says they need only move somewhere where they're not known, using the money they'll be getting from the legacy.
At this point Boyle admits that they will not be getting any money, since Bentham wrote the will incorrectly: instead of naming Boyle and the other beneficiary he simply wrote "first cousin" and "second cousin," so now all cousins can claim a portion of the money and the legacy has become worthless. Johnny is outraged at his father, infuriated that he ran the family into debt so he could drink every day. Juno tries to placate him, but he blames her too, for not checking up on Boyle and looking after the money.
There is a a knock at the door and two furniture men enter to take back the family's furniture. Juno leaves to find Boyle, Mary returns, and Johnny chastises her.
Jerry enters, looking hopeful. He tells her her mother has told him everything, and that he loves her more than ever even though she had left him for another man. When he learns that she is pregnant, however, he expresses his pity and leaves. As he goes, Mary recites for him some verses from his lecture on Humanity's Strife with Nature, whose message is that the world is both a beautiful and a horrific place.
The furniture men return, saying they can't wait for Boyle any longer, and start carrying some things out. Johnny chastises Mary again for telling of the shame she has brought upon the family, and she rushes out.
The votive light flickers for a moment and then goes out. Johnny cries in fear, to the disgust of the furniture man. He says he feels a pain in his breast, as if he were getting hit by a bullet. At that moment two Irregulars enter the room. One orders the furniture men to face the wall, while the other tells Johnny to come with them. We learn from their conversation that Johnny had given away Robbie Tancred's hiding place to the gang who killed him. The Irregulars drag Johnny away, and the curtain falls.
When the curtain rises again, most of the furniture is gone. Juno and Mary sit by the fire, waiting for Johnny. Mrs. Madigan comes in and tells Juno that two policemen want to speak with her; they've found a man they think is Johnny. Mary laments that there must not be a god or he wouldn't let such things happen, but Juno responds, "Ah, what can God do agen the stupidity o' men!" (70.)
Juno decides that she and Mary won't return to the tenement. They will live with Juno's sister until Mary has her baby, then work together to raise him or her. She urges Mary to come see Johnny's body, then changes her mind, chastising herself for her selfishness. She repeats Mrs. Tancred's words from when she lost her son, praying for humanity to lose its hatred and receive eternal love. They all exit the stage slowly.
In the last scene, Boyle and Joxer, both very drunk, return to the apartment. Boyle wonders aloud what the policemen were doing with Juno and Mary. He has just one coin left and drunkenly wonders where the chairs have gone. He supposes he can join the IRA if need be. The play ends with Boyle's characteristic saying: "I'm telling you... Joxer... th' whole worl's... in a terr... ible state o' ...chassis!" (73.)
The dichotomy between Juno and the "paycock" continues in Act III as we see how differently the two respond to suffering. While Boyle can think only of the effect Mary's plight will have on him and his reputation, Juno points out the ordeal their daughter will have to go through. Boyle is not even aware that Johnny has been killed, having left to escape his troubles through drink. Juno, however, undergoes a spiritual transformation as she realizes how selfish she has been in the past: “I forgot, Mary, I forgot; your poor oul’ selfish mother was only thinkin’ of herself… maybe I didn’t feel sorry enough for Mrs. Tancred when her poor son was found as Johnny’s been found now - because he was a Die-Hard." (71-2.) Thus strengthened, she decides to respond to tragedy in the way which will cause the most good, by leaving her lazy husband and instead helping Mary to raise her child.
Once again, we see how money affects the way that people treat one another. Boyle was practically a celebrity when his neighbors thought he would be inheriting a fortune; now that they realize the legacy is gone, they have no mercy in taking as readily as they previously gave.
The tone of Act III is noticeably darker than the rest of the play, emphasizing the tragic elements of the tragicomedy. Even amongst the suffering, however, there are humorous moments. Joxer's behavior as the truth about Boyle is discovered is very funny; he sides with Nugent against Boyle, then a moment later expresses his outrage with Boyle against Nugent. We laugh, too, when he steals Boyle's bottle of stout and then goes along with the story when Boyle blames it on Nugent. At the same time, the tragedies become more pronounced. Johnny, who should have been considered a hero for his role in the Easter Rebellion, again reveals his cowardice as he is taken away. Men who should have been supportive reveal their narrow-mindedness as they turn from Mary in her plight. Nationalism seems to lose its purpose as the tragic consequences of war become clear, and the dehumanizing power of poverty reveals itself again.
O'Casey continues his excellent stagecraft in this act, with actions becoming more symbolic. The extinguishing of the votive candle is a powerful foreshadowing of Johnny's death. After the tragic event, Juno stands beneath the picture as she invokes the Virgin, a compelling juxtaposition of mothers who have lost their sons which may suggest Juno's own godliness. Arguably, O'Casey achieves his finest moment when all of the upholstered furniture purchased on credit is taken away, so that in the last scene Boyle and Joxer stagger into a stark, empty room - a powerful symbol of the chaos to which Boyle refers in the last line.
As in the rest of the play, the language reflects urban life in the Dublin tenements and also makes us laugh. Nugent says he hasn't received even a "red rex" (penny) and that Boyle wouldn't be getting even a "make" (halfpenny). Joxer uses hyperbole and literary allusion to comic effect when he lets Boyle blame Nugent for stealing his bottle of stout, saying, "Ah, man's inhumanity to man makes countless thousands mourn!" (57; a quote from Robert Burns.) The malaprops continue as well, such as Mrs. Madigan's use of the word "formularies" (58) in place of preliminaries or formalities.