The mayor leaves. Mrs. Stockmann tries to convince her husband that he doesn't have the power to take on his brother. She urges him to remember his family, but Petra protests. Dr. Stockmann explains that he will never be happy if he bows to the mayor's demands, and when his family is mentioned, he explains that he will never be able to look his sons in the eyes if he doesn't keep trying.
The plot of this play traces the changing popularity of Dr. Stockmann's proposal. In the first act, everyone seemed to support it. In this act, however, the audience sees how the townspeople react in different ways to his proposal to fix the baths.
Morten Kiil thinks that the proposal is a joke. He notes that the bacteria that are supposedly polluting the water are invisible. Even Hovstad's enthusiastic support foreshadows danger. He wants to use the report to topple the local bureaucracy. He seems to be interested in how useful the report is to him. In other words, if someone can convince him that publicizing the report is not in his best interests, he might not print it. Aslaksen supports the move to fix the baths, but already he shows himself to be prudent to a fault. If the mayor can make the project look risky or dangerous to Aslaksen, he might withdraw his support.
The mayor raises a number of solid complaints against Dr. Stockmann's proposal to fix the baths. It is easy to root for the doctor and to see the mayor as a corrupt politician, but it is not Ibsen's intent to create a play of good versus evil. The doctor is perhaps too surprised by the mayor's resistance. He wants complete agreement or he is ready to go to war. Furthermore, it should be remembered that the play was written in the late nineteenth century and that it is not surprising that people are skeptical when told about bacteria. The doctor also appears to have a long history of coming up with eccentric plans.
The doctor, however, clings to his idea, just as he clings to his moral obligation to publicize his findings and to save the people from the consequences of bathing in polluted water. He is an idealist, but he is also an innocent. He doesn't understand Hovstad's interest in manipulating the pollution discovery to other purposes, and he was unable to predict the many economic and political consequences of his findings. This play, in many ways, is about the extent to which individual innocence can survive in modern society.