In Henrik Ibsen's play A Doll's House, Nora resolves to leave her husband and children, however the reasons by the middle of the play are very different from her reasons at the end of the play.
It becomes evident by Act II that if Krogstad reveals to Nora's husband her forgery, Nora believes it will be necessary for her to leave her husband and children. However, her first inclination is to commit suicide in order to rescue her husband and children from damage to their reputations. We know that Nora has resolved to commit suicide due to her conversation with Krogstad in which he tries to persuade her that it is unnecessary and would not ultimately help (Act. II). Furthermore, in Act III, while Torvald is in his study reading Krogstad's letter, Nora declares "Never to see him again. Never! Never! Never to see my children again either--never again. Never! Never!" and further cries out "Ah! the icy, black water--the unfathomable depths" (Act III). Both of these lines indicate with certainty that not only had Nora resolved to leave her husband and children that night, she planned to leave them by throwing herself into the river to commit suicide in order to rescue her husband and her children from scandal over her forgery.
However, Nora has a slight change of heart after Torvald is angered by the letter. Torvald argues that Nora is not fit to raise the children because she is a hypocrite, a liar, and a criminal. Because of her lack of religion and morals, he says that he dare "not allow [her] to bring up the children" (Act III). Torvald's anger and narrow minded opinion makes her realize things about herself, her husband, and the ways of the world that she had not yet realized.
By the end of the play, Nora agrees with Torvald that she is not fit to raise the children, but she agrees for different reasons from her husband. Nora realizes that she is very naive about the ways of the world and even about her own thoughts and opinions. She declares to Torvald that when she was with her father she merely accepted her father's opinions and concealed her own. Similarly, in her marriage to Torvald, she adpated her husband's tastes, rather than exploring her own (Act III). Thus, Nora has never explored her own opinions, thoughts or tastes and feels uneducated as a result. Nora believes that before she is ready to be a wife or a mother, she must first educate herself.
Therefore, by the middle of the play, Nora had decided to leave her husband and children by committing suicide in order to protect them from slander. But by the end of the play, Nora again decides to leave her children and her husband because she realizes that she is indeed not fit to be either a proper mother or wife due to her naivete and lack of self-education.
It is not that Nora is explicitly leaving her children, but she believes she has done nothing wrong in helping her husband, protecting her father, that she leaves. She finally understands and realizes that the male dominant society has been controlling her with their rules and laws, not allowing them to reach a woman's full potential.
A woman may be able to have an education, but it would not be according to her ability, but her gender and role in society. Even if she has natural talent as a Chemist, there is no way that a woman would be able to achieve that, because she is a female.
Nora also realizes that she has spent so much time being pampered and pleasing Torvald with her little dances and flirty behaviour, that she has not gotten to know Torvald. Likewise, Torvald does not know Nora as a person, only as the doll and child act she puts up for him. It is this final realization that makes Nora leave her house and become a proper individual of society.