In "A Doll's House," how does Krogstad and Mrs. Linde's relationship serve to emphasize certain qualities in the Helmers' marriage?
In "A Doll's House," there are certain conventions and expectations which are prevalent throughout. Nora would never be permitted to borrow money without her husband's consent and she would not be allowed to work unless she was either unmarried or a widow. Accordingly, Nora has had to take extraordinary steps to secure a loan, without Torvald's knowledge and to work and save what she can so as to be able to pay off the loan. It is almost paid off but now Krogstad (who arranged Nora's loan in the first place and knows her secret) has re-emerged and threatens Nora and Torvald's seemingly perfect life as he has threatened to expose her. At first, Nora is confident that her husband "will of course pay you off at once," if necessary but she would rather he did not find out about it this way.
Nora and Torvald's marriage is based on his need to protect his "little spendthrift," whom he treats like a child, and her willingness to reduce herself to his "little squirrel," subject to his rules, and with no apparent contribution to make to family business. Torvald is condescending and is fixed in his belief of how a family should be run. Only when Krogstad and Mrs. Linden are reunited, is Nora forced to face the fact that her own marriage does not have a solid foundation. Torvald feels so strongly about what Krogstad may have done (which is ironically exactly what Nora has done) that he suggests that, "Every breath the children draw contains some germ of evil." Torvald says that Krogstad is "morally ruined" for failing to admit his wrongdoing and face the consequences. Nora is terrified at the thought that she may be corrupting her own children. This reveals the complete disparity between Nora and Torvald and foreshadows what will follow.
Torvald says that "my shoulders are broad enough to bear the whole burden" because he does not think that anything Nora has done could ever be significant. His words are hollow and do not provide Nora with sufficient confidence to tell him everything. Their marriage has always been based on Nora's complete submission. On the other hand, even though Mrs. Linden has only just returned to the town, she is already confident that she can talk to Krogstad, and she tells Nora that she will convince him to demand his letter back. Nora begins to feel more confident, waiting for the "miracle."
Krogstad and Christina are honest with each other, and this emphasizes the lack of faith in the Helmer marriage. Furthermore, even though they have hurt each other in the past, if they are to make a new start, it will be on equal footing. This is in stark contrast to Torvald and Nora and highlights their insecurities. They cannot make a new start because they still cannot be wholly honest and Torvald cannot see his own failings. He cannot see Nora's worth.
Krogstad and Christina may still have some reservations about their future but they prove their devotion to each other. Christina is prepared to withdraw her request to Krogstad to prove that she is genuine, and at the same time, Krogstad will withdraw the letter if it is what Christina wants. The decision to leave the letter, if the Helmers' are to have any chance of repairing their marriage, is based on Christina's view. Unfortunately, the Helmers' do not have the foundation to recover from.
The relationship between Krogstad and Mrs. Linde illustrates how forgiveness can heal relationships and bring people together. Krogstad and Mrs. Linde had a relationship many years before, but Mrs. Linde married someone that would financially support her mother and brothers. She did what she had to do for her family's sake, and years later, Krogstad was able to forgive her and move past the pain to go forward in their relationship.
This is a direct contrast to Nora and Torvald. Nora lied and forged for the good of her family, but Torvald is unable to forgive her and Nora realizes that her marriage cannot be healed.