As the play begins, Dr. Stockmann is hosting a dinner party; among the guests are his brother Peter (who happens to be the town's mayor) and Hovstad, the editor of the local newspaper. Peter asks Thomas about a rumor going about town, that he's writing a critical article for the paper about the spa. Thomas avoids telling his brother what the article is about and, after Peter leaves, the doctor's daughter Petra brings in the mail. There's a letter from the lab containing the test results; as Stockmann feared, the water at the spa is contaminated with bacteria. Hovstad agrees to print his article about the dangers of the spa but points out that this will probably result in the spa being shut down. This will deliver a crippling blow to the local economy as a lot of its income is derived directly or indirectly from the spa and its visitors. Dr. Stockmann realizes this, but ultimately, keeping people safe from contaminated water trumps concerns about the economy.
Act III opens in the newspaper office, where Hovstad and Aslaksen are having second thoughts about printing the article. They question whether this is the right way to expose the government, considering the harm which it will inflict upon the town's economy. They ultimately decide against printing Dr. Stockmann's article. Instead, they agree to print a statement by Mayor Pete, reassuring the public that the spa baths are completely safe. Since he can't get his article published, Stockmann decides to call a town meeting to inform the public about the bacteria infested water. His wife Katrine worries about what this will do to his reputation and career, but staunchly supports him.