Act III is a single scene that takes place the morning after the chaotic public meeting. Dr. Stockmann’s living room has been vandalized. The windows are shattered, stones lie scattered across the floor, and the house is cold and disordered. Dr. Stockmann moves through the room collecting the stones like “sacred relics.” Another rock crashes through a window while he works, revealing that even children have joined in attacking the family. Catherine expresses disbelief at how quickly public opinion has turned, but Dr. Stockmann sees it as proof of how easily corruption spreads through society.

The family’s isolation becomes clear as the glazier refuses to repair the windows out of fear of public backlash. Next, a letter arrives informing them that they’re being evicted, confirming Catherine’s suspicion that “the town must be ready to murder [them]” (66). She grows increasingly anxious about their safety and future, while Dr. Stockmann tries to reassure her by suggesting that they emigrate to the United States, though even he admits uncertainty about whether conditions would be better there. The damage to their social standing continues when Petra returns home, having been dismissed from her teaching position due to pressure from “big patriots with their anonymous indignation” (68), who sent unsigned letters to the school demanding that she be fired due to her “radical opinions.” The family recognizes that the entire town has turned against them.

Captain Horster enters, offering calm support. However, he reveals that he, too, has suffered consequences for helping Dr. Stockmann: He has lost his position as a ship captain because of his association with the family. Despite this, Captain Horster remains composed and loyal.

Peter then arrives. He confirms that Dr. Stockmann has been dismissed from his official position and informs him that the townspeople are signing a petition pledging not to use his medical services. Peter claims that he doesn’t want to “ruin” his brother but insists that public opinion leaves no alternative. He offers Dr. Stockmann a way out: If he signs a statement retracting or softening his claims about the polluted baths, he will be reinstated, and the town will “gradually make all the improvements” so that the baths will no longer be poisoned (71). Dr. Stockmann rejects this proposal, insisting that he can’t compromise while people are being harmed.

Peter escalates the conflict by revealing that Morten Kiil has been buying shares in the baths. This creates the appearance that Dr. Stockmann’s “relentless campaign to destroy confidence in a corporation” is a scheme to lower stock prices for financial gain (72). Dr. Stockmann is shocked by this implication, but Peter threatens legal action for conspiracy if he continues his campaign.

After Peter leaves, Kiil himself enters and explains his actions. He admits that his tannery is the source of the pollution and that he bought the shares to protect his family’s reputation. By tying the family’s financial future to the baths, Kiil attempts to pressure Dr. Stockmann into retracting his claims. He argues that there’s room for doubt in the scientific evidence and urges Dr. Stockmann to reconsider his conclusions. Dr. Stockmann struggles with the moral dilemma, recognizing that his principles now directly endanger his family’s livelihood. He concedes that “nothing is a hundred per cent on this earth” as Kiil makes his ultimatum clear (76): Either Dr. Stockmann retracts his claims, or the family will lose their inheritance. Dr. Stockmann refuses to compromise his morals, and Kiil leaves, telling his son-in-law to retract the accusation and clear Kiil’s “good name” lest the shares be given to charity.

Shortly afterward, Hovstad and Aslaksen arrive. They reveal that they now know about Kiil’s stock purchases and reinterpret Dr. Stockmann’s actions as self-interested. However, they offer to restore his reputation if he supports them financially. They propose launching a campaign to present him as a hero who acted for “absolutely scientific, public-spirited reasons” (79), but only if he (or his father-in-law) helps cover the newspaper’s losses. Their plan avoids addressing the actual problem of the polluted water, focusing instead on managing public perception. Dr. Stockmann realizes that they’re attempting to manipulate him and rejects their offer, accusing them of corruption and blackmail. In response, Hovstad accuses Dr. Stockmann of being an egotistical “demon” who is willing to ruin his own family.

The confrontation intensifies when the Stockmann children return home. One of the sons has been injured after being attacked by other boys who called their father a “traitor.” Dr. Stockmann comforts his son but becomes resolute in his stance. He openly declares himself an “enemy of the people” (82), embracing the label imposed on him. He then drives Hovstad and Aslaksen out of the house in anger, rejecting any compromise. 

As more stones are thrown and the hostile crowd gathers outside, Catherine suggests that they flee, but Dr. Stockmann refuses. Instead, he decides that they will stay and resist. He states that they will “live through this” (84). He proposes starting a small school to educate independent thinkers. The scene ends with the family united but isolated, facing the threat of violence from the crowd outside. Dr. Stockmann asserts that their strength lies in their willingness to stand alone for the truth. They are the strongest people in the world, he claims, but “the strong must learn to be lonely” (85).