The play is presented in three acts, all of which take place in the parlor of an upper-middle-class household. It begins with the entrance of Nora Helmer, a young, happy wife and mother of three children, followed by a porter toting a Christmas tree. Her husband, Torvald, calls out to her from his office, checking to see if his "little squirrel" has come home; then he asks not to be disturbed. A little while later, the audience sees the affectionate couple interact for the first time. Torvald believes his wife is wasteful with money and teases Nora for spending too much, but he understands she has extra expenses at Christmas time. This establishes their relationship: Nora begs, Torvald indulges. Nora excitedly shows Torvald her presents for the children and requests money wrapped in paper for her own Christmas present. Torvald has no idea Nora needs money for a loan she borrowed without his consent: she has been working in secret to pay back her lender.
A childhood friend of Nora's drops by, and the two women discuss how their lives have changed since they last saw each other ten years ago. Christine is now a childless widow, worn out and overworked. Nora brags about Torvald's new position at the bank and offers to convince him to hire Christine. Nora then describes how she saved Torvald's life early in their marriage by providing the money they needed to spend a year in Italy. She lies in saying that she inherited the money from her father. When Christine offends Nora by suggesting she's had an easy life, Nora divulges that she took out a loan without Torvald's consent to pay for the trip and must secretly pay it back. Christine calls Nora "mad" and "imprudent," but Nora refuses to tell her who loaned her the money.
Then another person from the Helmers' past arrives at the home. Once part of Torvald's social circle and now working far below him at the bank, Nils Krogstad arrives to meet with Torvald. Krogstad's presence makes Nora and Christine nervous, and it is soon revealed that Krogstad is Nora's moneylender. Dr. Rank, a close friend of Torvald and Nora, comes into the parlor after passing Krogstad in the hall. He gossips about Krogstad's bad reputation for being a crooked lawyer caught up in a scandal years ago. Torvald meets Christine and says he is willing to give her a position at the bank. Torvald, Dr. Rank, and Christine leave Nora as the children arrive with their nurse.
Krogstad slips back into the house and catches Nora by surprise. He suspects Torvald will replace him at the bank with Christine, whom he has known from the past. Krogstad wants Nora to influence Torvald to let him keep his post at the bank. He threatens to tell Torvald about the loan as a means to fight for his position. When Nora refuses, Krogstad reminds her that she has committed fraud by forging her father's signature as surety for the loan. Krogstad explains to Nora that by dating the loan five days after her father's death, she has committed an illegal act. He assures her she will be found guilty if he takes her to court.
When Torvald returns, Nora tries to persuade him not to fire Krogstad, but Torvald is resolute. To him, Krogstad is a scoundrel whose presence makes Torvald physically ill. The next day, Nora tries again, infuriating Torvald into firing Krogstad immediately instead of waiting until the New Year. Increasingly desperate, Nora considers asking Dr. Rank for help, but changes her mind when the doctor confesses his love for her. Krogstad returns to tell Nora he has decided not to expose her publicly, only to Torvald. He drops a letter about the loan and forgery into a locked letterbox outside of Torvald's office, to which Torvald has the sole key.
In a panic Nora tells Christine that Krogstad is her moneylender. Eager to help, Christine rushes out to convince Krogstad to recall the letter. To distract Torvald from reading the letter, Nora begs him to help her rehearse a dance for an upcoming costume party. Torvald, under the misconception Nora fears Krogstad will take revenge on Torvald for firing him, suspects Krogstad has left a letter in the box, but he agrees to wait to read it until after the party. Torvald promises Nora that whatever happens, he will share every burden with her as a true husband should. Nora finds hope in his words.
While Nora and Torvald are upstairs at the neighbor's party, Christine meets privately with Krogstad. She expresses her desire to begin a new relationship with him even though she chose another man with better prospects when they were younger. Joyous at the idea of a second chance with Christine, Krogstad offers to recall his letter to Torvald, but Christine tells him not to, believing honesty will bring complete understanding into Nora and Torvald's marriage. Later that night, when Torvald reads Krogstad's letter revealing the loan and forgery, he completely repudiates his wife, saying they will only appear as if they are still married; that he will allow her to live in his house, but he will not allow her to bring up the children, nor will he love her.
A new letter from Krogstad arrives. He has forgiven the loan and given back the bond, which Torvald burns in the fire. Ecstatic that his reputation will not be damaged, Torvald forgives Nora everything she has done. He determines to become her teacher, father, conscience, and will. Nora finally understands her husband's self-preserving concerns, and that he does not truly love or understand her. She will always be nothing more than his doll. At that she decides to leave him, educate herself, and make her own way in the world.
The play famously closes with the slamming of a door.