Nora borrows 250 pounds so that she and her husband can spend a year in Italy, a journey that would save her husband's life from the clutches of illness. In doing so, she forges the date appearing beside her father's signature on the legal tender of the loan, and to pay for it, she tucked away part of her household allowance and did odd jobs behind her husband's back.
The relationship between the couple is put to test when Torvald threatens to dismiss Nils Krogstad, one of the clerks in the bank that he manages. Incidentally, Krogstad is also Nora's creditor. Krogstad attempts to blackmail Nora into convincing her husband to retain Krogstad in his position in the bank; in return, the secret of the loan will remain a secret. Nora fails to do so, and tries to scheme and plan to avert the impending disgrace. She even thought of going away so that her family would be spared the humiliation (Sparknotes, "Doll").
Among the means that came Nora's way to hide the secret is a promise of help from her girlhood friend Christine Linde. Nils Krogstad is Mrs. Linde's former sweetheart; she thought she could convince him to keep the secret. But when the time came, Mrs. Linde reneged on her promise.