HELMER: "A guilty man like that has to lie and […] has to wear a mask in the presence of those near and dear to him, even before his own wife and children. […] the children—that is the most terrible part of it all, Nora." (1.467)
It's ironic that Torvald is saying this in front of his wife, who has deceived him so often.
HELMER: "My little songbird must never do that again. A songbird must have a clean beak to chirp with—no false notes!" (1.435)
The danger of Torvald finding out about Nora's deceit is the essential tension that drives most of the play.
HELMER: "Hasn't Miss Sweet Tooth been breaking rules in town today? […] taken a bite at a macaroon or two?" NORA: "No, Torvald." (1.55-1.62)
Nora lies on about every page of the play. This is the first one of which the audience is aware. It seems pretty innocent to lie about cookies, but it hints at a much larger gulf in their marriage.
NORA: "It was necessary he should have no idea what a dangerous condition he was in. It was to me that the doctors came and said that his life was in danger." (1.193)
It's interesting that all Nora's lies to Torvald stem from an act of love.
HELMER: "How I am punished for having winked at what he did! I did it for your sake, and this is how you repay me." (3.236)
Ah, so Helmer's record isn't as spotless as he makes it out to be. He admits here that he ignored some of Nora's father's wrongdoing.
HELMER: "What a horrible awakening! All these eight years—she who was my joy and pride—a hypocrite, a liar—worse, worse—a criminal!" (3.236)
The fact that Nora did all these things for him seems to be completely lost on Torvald.
HELMER: "What is this? Someone has been at the lock. […] Here is a broken hairpin. Nora, it is one of yours." NORA: (quickly) Then it must have been the children—" (3.198-3.201)
Down to the very end, Nora lies to her husband. We wonder why she still keeps it up by this point. He's going to find out everything in about thirty seconds anyway.
HELMER: "I must try and appease [Krogstad] some way or another. The matter must be hushed up at any cost." (3.242)
Isn't Torvald being hypocritical here? Isn't covering up Nora's indiscretion deceitful as well?
HELMER: "I ought to have foreseen it. All your father's want of principle—be silent!—all your father's want of principle has come out in you." (3.236)
Where else in the play are there ideas of inherited guilt?
Mrs. Christine Linde
MRS. LINDE: "they must have a complete understanding between them, which is impossible with all this concealment and falsehood going on." (3.78)
Christine seems to hope that the truth will heal the Helmers' marriage, when in fact it destroys it.