It is the night of the party, and dance music can be heard from upstairs. Nora and Torvald are at the party and Mrs Linde sits alone in their apartment, waiting for someone. Krogstad arrives; it is he whom she was expecting. He reproaches Mrs Linde for jilting him, but she says she had no choice; she had family to support and he was poor. She tells him that only today did she discover that it is his job that she is due to take. He asks her if she will give it back to him, but she says this would not benefit him. She needs someone to look after, and suggests that they get back together. He cannot believe that she can overlook his past life, but she has faith in his essential goodness and believes his previous claim that he would be a better man if he were with her. He is delighted. He realizes that she knows what steps he has taken with the Helmers, and suggests that he ask for his letter back. But Mrs Linde insists that Torvald must know Nora's unhappy secret. They must give up concealment and grow to a full understanding. Krogstad leaves. Mrs Linde is overjoyed that at last she will have someone to care for.
Torvald enters, dragging Nora in with him. She had wanted to stay at the party but he had insisted that they come home. Mrs Linde explains her presence by saying she wanted to see Nora in her dress. Torvald shows off his wife's beauty but censures her "self-willed" behavior. When he leaves to light candles, Mrs Linde quickly tells Nora that she has nothing to fear from Krogstad, but that she must tell Torvald the truth, or the letter will. Nora says that she now knows what she must do.
Mrs Linde leaves. Torvald is glad of it, since his desires have been aroused by Nora's dancing and he has hurried her back home in order to make love to her. He tells her that he has been fantasizing about her all evening, thinking of her as his secretly promised bride. Nora rejects his advances. Just as Torvald is voicing disbelief that she could refuse him his conjugal rights, they are interrupted by Dr Rank. He has called by on his way home from the party, ostensibly to borrow a cigar. In a coded conversation that Torvald fails to understand, Nora asks Dr Rank about the results of scientific investigations he has been performing. Dr Rank knows that she is inquiring about medical tests. She understands his reply to mean that he is certain to die very soon. During their playful discussion about what costumes they will wear to the next party, Dr Rank suggests that she go as a good fairy - but dressed just as she is normally. He says that he will wear a big black hat that will make him invisible. Nora understands the significance of his words and of the two cards with black crosses that he drops into their letterbox as he leaves: both refer to his imminent death.
Torvald notices that someone has been trying to pick the lock of his letterbox. Nora blames the children. Torvald finds Dr Rank's cards and realizes that he is announcing his own death, which he finds "an uncomfortable idea." Torvald embraces Nora and reflects that now they will be thrown entirely upon each other. Nora draws away and firmly asks him to read his letters. He takes them into his study.
Nora puts on Torvald's cloak and is apparently about to rush off and drown herself when Torvald comes in with Krogstad's letter in his hand and asks if the contents are true. Nora confirms that it is true, that she has loved him more than anything else in the world. Torvald dismisses this as "excuses." He demands an explanation but gives her no chance to give one. He accuses her of disgraceful behavior and says she has no sense of religion, morality or duty - all traits he believes she inherited from her father. She has, he says, ruined his life by putting him at Krogstad's mercy. Nora says that when she is out of the way, he will be free, but this only angers him more, as Krogstad could still make the affair known and imply that he was a party to Nora's forgery. Torvald plans to appease Krogstad. He wants Nora to remain in his house and pretend that all is as before between them. But the appearance of a marriage will be all that remains. She will not be allowed to bring up their children.
A maid arrives with a letter for Nora. Torvald seizes it and opens it. It is from Krogstad, who has returned Nora's bond (an IOU) with a letter of repentance. Torvald changes his attitude towards Nora, saying that he has forgiven her and knows that she acted out of love for him; she chose the wrong means because of her lack of knowledge and helplessness, a trait that he finds attractive. He argues that, by forgiving her, he feels he has given Nora a new life so that she is now both his wife and his child. But Nora says that Torvald has never understood her and that, until now, she has never understood Torvald. As he continues to address her as a little bird that he has to rescue, she takes off her fancy dress. Now in everyday dress, she wants to discuss their marriage. She tells him that this is their first serious talk in eight years. She says that both her father and Torvald have treated her like a doll-child, with no opinions of her own, and have only played with her. Both men have committed "a great sin" against her. It is Torvald's fault that she has made nothing of her life.
Torvald grudgingly admits that there is some truth in what she says. He says that playtime is over, and now he will start to educate her. But she replies that he is not the man for the job, which is why she is leaving him; she must educate herself. Torvald asks how she can neglect her sacred duty as a wife and mother. She says that she has a more important duty, to herself as a human being. She intends to look into religion and morality and form her own philosophy, rather than accepting the dictates that society has imposed upon her. Torvald believes she is ill or has lost her mind, but she says her mind has never been so clear. She no longer loves Torvald, as he is not the man she thought him. She had believed that a wonderful thing would happen: that Torvald would stand up to Krogstad's threats, challenge him to do his worst, and take the entire blame upon himself, in order to shield her. She would not have accepted such a sacrifice on his part, and indeed, she had wanted to kill herself to prevent his having to make it. But she has been disillusioned by the fact that he never intended to make it.
He replies, "no man would sacrifice his honor for the one he loves." Nora points out that thousands of women have done so. She, of course, is one of them. To make things worse, as soon as his fear about the damage that Krogstad's revelations might do to him was over, he wanted to pretend that nothing had happened, and for her to return to being his fragile little doll. He now appears like a stranger to her, and she cannot spend another night in his house. She will leave her children in the care of the Nurse, who she believes will do a better job of bringing them up than she could at the moment. She gives him his wedding ring back and asks for hers. She forbids him even to write to her. He asks if they can ever be together, but she says that the most wonderful thing of all would have to happen first: they would both have to have changed so much that their life together would be "a real marriage." In his despair, Torvald clings to a last hope that this most wonderful thing might still happen. But his hope is shattered by the sound of Nora shutting the door as she leaves.
Torvald's superficiality and inability to consider others' interests are highlighted in his suggestion to Mrs Linde that she should embroider rather than knit, as it is so much more becoming. He shows no regard for the fact that knitting is a more practical skill for someone who has struggled financially.
Nora and Dr Rank feel that they must shield Torvald from knowing about Dr Rank's imminent death by talking in a code that Torvald fails to understand. While Torvald chuckles over his "little" wife's talking of Dr Rank's scientific investigations, Dr Rank knows that she is asking him whether he is soon to die. A more serious conversation and a more momentous event in Dr Rank's life cannot be imagined, yet his friend Torvald, trapped in his fantasy world of skylarks and squirrels, has no clue of its true meaning.
An exchange between Nora and Dr Rank brings home the contrast between their relationship and that of Nora and her husband. Dr Rank and Nora see each other relatively more truthfully. When Nora asks Dr Rank what he and she shall wear at the next fancy dress ball, he says that she shall go as a good fairy, but that she will not need a costume, just her everyday clothes. This contrasts sharply with Torvald's erotic fascination with Nora's fancy Tarantella costume, which he chose. Dr Rank sees Nora's goodness in her essence, not in her appearance.
Dr Rank adds that he will go to the next fancy dress ball in a big black hat that will make him invisible - a reference to his death, which passes over Torvald's head but which Nora understands. In a gesture with symbolic resonance, Nora offers Dr Rank a light for his cigar, an image of spiritual illumination that contrasts with the black hat of death.
Nora has playful, coded conversations with both Torvald and Dr Rank, but they are very different in nature. Her "little squirrel" conversations with Torvald are a kind of lie which hides the deeper truth of her nature and of their marriage. These are not conversations between equals: Torvald thinks he is patronizing Nora, when in fact she is the one protecting him from harsh reality. Her conversations with Dr Rank are between equals: each understands the other, and profound truths are communicated and revealed by means of the code. Again, however, the effect is to shield Torvald - this time from the unpleasant reality of Dr Rank's imminent death.
Another contrast between the two men is that Dr Rank has loved Nora with a selfless, unpossessive love, even while she has been married to his friend and even now that he is dying. This seems quite unlike Torvald's love of Nora as a beautiful possession - "Why shouldn't I look at my dearest treasure? - at all the beauty that is mine, all my very own?" We have already seen that he is unwilling to share any part of her, forcing her even to refrain from mentioning her other friends to him.
The crisis in the Torvald-Nora marriage comes at the end of the Act. Torvald discovers that Nora has made huge sacrifices to save his life, even committing a crime in the process, but he does not respond with gratitude, understanding or compassion. All he can think about is his own public image, which he accuses her of ruining. He wants to preserve a sham marriage, just to maintain the appearance of respectability. Nora realizes that she has been wrong about Torvald; she had thought that finally, he would rescue and protect her, but in fact, he fails to consider her welfare at all. He shows himself to be selfish, petty and ungenerous. She had trusted in his great love for her to make everything right, but he has betrayed this trust.
Torvald's explanation for refusing to take the blame, that a man would never sacrifice his honor for love, reveals the double standards that were conventionally applied to women as against men. Nora replies that "hundreds of thousands of women" have done just that. Both Nora and Mrs Linde have sacrificed themselves for their loved ones. Nora seems justified in her belief that Torvald should take responsibility for her, since she is expecting him to do no more for her than she has already done for him.
Even after he knows there is no danger from Krogstad, Torvald remains unwilling to allow his wife to grow into her own strength. He cannot relate to Nora as she is, only to her play-acted role. He wants her to remain a little fragile bird that he needs to rescue. When she refuses to resume this role, he thinks of a new one for her: that of pupil to his teacher. Earlier in the Act, when she danced the Tarantella, she had played another role for which Torvald had dressed and coached her, that of a sultry Italian seductress. But she knows that she can no longer live as a doll; she cannot continue to have her life defined by the men who purport to love her. Her new self-knowledge is symbolized by her removing her fancy dress as she distances herself from his attempts to confine her in the roles he has defined for her. She decides that she herself must define who she is and what she does, and leaves Torvald and her children. It is no longer enough for Nora to live the life of appearances that she maintained in collusion with Torvald. She chooses to forge a life that is more in tune with her true nature.
It would be unfair simply to blame Torvald for the catastrophe of their marriage. Nora has colluded in Torvald's and her father's treatment of her as a "doll" with no opinions or identity of her own. We have seen her manipulate Torvald by concealing her strength and playing the helpless "little squirrel" and "little bird" to his paternal rescuer. She has also kept secret from him anything that would challenge his view of her. But, as the story of the play has made clear, women were not educated or otherwise prepared for taking on the responsibilities of life. Where they did gain some self-sufficiency, as with Mrs Linde and the Nurse, it often involved great hardship and sacrifice. As a man accustomed to responsibilities, Torvald should have been aware that along with the perks of his chosen role (having a submissive wife and plaything) come duties: to support his wife in her hour of need. Torvald fails in this duty and breaks the implicit contract of the marriage.
Mrs Linde is a foil (contrast) to Nora in that her route to self-fulfiment is the reverse of Nora's. Nora chooses to leave her family, but Mrs Linde, who has led just such an independent life as the one Nora is embarking upon, decides to give it up to look after the man she loves and his children. Some critics have commented that Mrs Linde's decision undermines Nora's and implies that Nora will come to regret her course of action. But this is to miss the point. Ibsen does not suggest that Nora's action in leaving her family is the only route for a woman to find her true identity. The important thing is that Nora, having lived in a sham marriage, makes a conscious choice of independence, and that Mrs Linde, having once given up the man she loved to support her relations, makes a conscious choice to look after him. Both are being true to themselves after a period of denying their true natures.