The Pastor leaves, and meanwhile Oswald has entered. He predicts Engstrand establishment will burn, just like all that remains of his father. He gathers his mother and Regina close to him, telling them that he needs a "helping hand." His mother says that she will now remove the basis of Oswald's self-reproach. She begins to tell how Oswald's father was full of "the joy of life"; she says he was full of untamed energy for which neither the small town nor she could provide an outlet for, so he had to take up with drunkards and become a broken man. She also admits that Regina "belongs in the house." Regina guesses her meaning immediately and asks to leave. She is bitter that Mrs. Alving hired her as a maid when she should have raised her as a gentleman's daughter. She goes to catch the Pastor and demand her inheritance from the money that would have gone to the orphanage and will now fund the saloon. She exits.
Oswald is mildly shocked but reminds his mother that he didn't know his father and, indeed, is just as troubled as before. When his mother tells him that every child should love his father, he asks how she can believe in such a "superstition." Mrs. Alving realizes that she is just propagating another ghost. She asks whether he loves her; he says at least he knows her, and that he is very thankful for all her help. Oswald admits that she has relieved him of his self-reproach, but he says nothing can alleviate his dread. She reassures him that soon the sun will come up. He sits her down, telling her that his dread results from the lapses he suffers, the fits of gloom that lurk in his mind and come upon him suddenly, rendering him helpless as a child. His mother tries to reassure him, saying that, as his mother, she is there to care for her child. But this is just what Oswald doesn't want. He savors the doctor's description of his illness as a "softening of the brain," finding the image charming—like red velvet curtains, supple when stroked.
Mrs. Alving is horrified. Oswald blames her again for scaring away Regina, who could have helped him. He says that the doctor predicted his next attack will be his last, and he shows his mother twelve morphine capsules—a lethal dose. He wants his mother to administer them when his attack comes—he knows that Regina would have done so had he asked her. Mrs. Alving finally promises to do so if necessary. He says that soon the sun will come and she will see the torment he suffers. She tells him that he has only been suffering from delusions and that now that he is home with his mother, they will go away. The sun rises over the glistening mountains, and she goes to turn out the light. Oswald says, "Mother, give me the sun." His muscles loosen and he slips in the chair. His mother panics and searches for the pills, screaming all the while.
Mrs. Alving finally tells the truth, if only partially. When she paid such close attention to Oswald's talk of "the joy of life," it was because she was finding an excuse for her husband's behavior. By explaining his sins by saying that he had too vibrant a spirit and no outlets for it, she is not only providing an excuse for the husband who made her miserable, she is shifting the blame to herself. She says that it was her boring sense of duty that stifled him, when, in fact, it was her sense of duty that made her stay with him and has driven her to preserve his reputation, even as she does with this speech.
Regina's reactions are not unpredictable. We are not surprised that she so unhesitatingly chooses to leave Oswald: throughout the play, she seems less interested in Oswald himself than in climbing the social ladder. Thus, she speaks in bits of French; thus, she is just as interested in charming the Pastor as Engstrand. Her actions also provide a new insight, however, as they also serve to expose and protest against Mrs. Alving's failure to think of Regina as a human. Instead, she wants to think of her as a child to be cared for and controlled.
Mrs. Alving's treatment of Oswald in this scene is similarly unrealistic. She continually tries to talk him out of his troubles; she will not accept that he is actually terribly ill. She mothers him, even and especially when he expresses disgust at being reduced by his illness to a childish level of helplessness. She also insists on the ideas of filial piety, of a son loving his father and of the nuclear family in general, that the Pastor has used on her throughout the play. When Oswald is able to call them superstitions—ghosts—she begins to recognize the horrible irony of her behavior.
If Mrs. Alving is inconsistent, so is Oswald. He reassures her but also threatens to leave and blames her for driving Regina away. In the end, he is right to doubt her. When he finally relapses, she is terrified, and the play ends before we learn whether she will give him the morphine or simply go mad herself.
The sunrise is a final symbol of light. It clears away the gloom; all the facts are on the table. Yet the result is not enlightenment but madness. Neither dark nor light is perfect. The dismal aspects of Norwegian society will persist. Oswald, who has always known the joy of living, now also knows the truth about the pain of living; under the weight of these combined truths he goes crazy.