Most of the conflict in Ibsen's A Doll's House is a result of the clash between the superficial appearance of the characters' lives and the deeper reality that they all must live with.
Nora lives a double life in many ways - she appears to Torvald to be a silly woman who only worries about what Christmas presents to buy the children and what to wear to the costume party. But, in reality, she is dealing with the repercussions of her forgery while working in secret to pay off her debt to Krogstad.
This conflict comes to a head when Nora realizes that Torvald does not love her more than he values his own personal honor. She realizes that the love she thought he had for her was a facade and that she was just another of his possessions. While she was willing to sacrifice her honor out of love for him, he was not willing to return the sacrifice.