Answer: Nora is always onstage, usually accompanied by one other character. Although sometimes there are multiple characters onstage at once, the majority of the play consists of the one-to-one conversations between Nora and either Torvald, Mrs. Linde, or Krogstad.
This structure allows the character of Nora to develop gradually. Torvald reveals his often patronizing attitude toward Nora and her spending habits, as well as his lack of faith in her ability to change her ways. Nora's interaction with Mrs. Linde reveals how passionately she looks forward to Torvald’s promotion. It also shows that she seems to regard his promotion as her own reward for boldly forging a signature on a loan to help him survive. Their conversation shows that while Nora is not evil, she does have a strong opinion of herself and is capable of taking bold steps, harboring secrets, and justifying those steps because she had good intentions.
Her interaction with Krogstad shatters the illusion that Nora can act on her own, break laws, and maintain her appearance of a controllable doll in a perfect dollhouse. His presence seems to start the rising action of real conflict that the other interactions set the stage for.