The most obvious character in Ibsen's A Doll's House that leads a double-life, hiding it with lies and deception, is Nora Helmer. And while her actions may not seem horrific to a modern audience (for Nora saves her husband's life and assumes the responsibility of repaying the loan), at the time the play was written, her actions would have been socially abhorrent.
At the play's beginning, Nora returns from Christmas shopping—the obedient wife. She and her husband talk about expenses. Torvald (treating her like a child) chastises her for her irresponsible spending habits, and then gives her extra cash.
...Come, come, my little skylark must not droop her wings. What is this! Is my little squirrel out of temper? [Taking out his purse.] Nora, what do you think I have got here?
[turning round quickly]. Money!
There you are. [Gives her some money.] Do you think I don't know what a lot is wanted for housekeeping at Christmas-time?
[counting]. Ten shillings—a pound—two pounds! Thank you, thank you, Torvald; that will keep me going for a long time.
Nora listens as he chides, and may seem flighty. It is only after the play continues for some time that we realize that Nora is pinching her pennies to pay back Krogstad, from whom she illegally borrowed money to take Torvald to a safer climate where he could regain his health: had Nora not done so, Torvald would have died. Torvald never suspects his wife's activities—or how clever she is.
It is not until the end of the play that Nora's "criminal" activities come to light. Torvald is obsessed with a fear that the public will find out what she has done, and his reputation will be ruined. He does not care that his wife saved his life. Ironically, it is Nora who has a much stronger sense of values than Torvald could ever have. While Nora does the unthinkable from a social and legal standpoint, her every move (at the time of her deception and after) has been with her husband's welfare in mind, rather than having a concern for the laws of an inflexible, male-dominated society. At the end, Torvald realizes he will not be ruined—pronouncing that they can put this "unpleasantness" behind them and return to life as usual:
The whole thing shall be nothing but a bad dream to me.
But Torvald's behavior has enlightened Nora. She can never go back to living the social lie that has been forced upon her: to be her husband's puppet—mindless and subservient, manipulated and controlled like a doll. The moment of her awakening is clear—Torvald fears his ruin at her hands; she sees that her husband cares not at all that she saved his life:
…Here you shall stay and give me an explanation. Do you understand what you have done? Answer me? Do you understand what you have done?
[looks steadily at him and says with a growing look of coldness in her face]. Yes, now I am beginning to understand thoroughly.
Nora's deception saves Torvald, but it also ultimately exposes society's lies, and enables her to see the rigid and unfeeling standards by which her culture governs its members—most especially its women. Nora sees her marriage is a lie—where she is not valued for the devotion she brings to the union, but for her ability to please society. Nora leaves at the play's end. She seems a compliant wife, but she deceives society to save Torvald from death. Though her deception seems unconscionable, the worse lie is the one she is forced to live—as if she were an automaton.