Which is the tone of this scene?

Mrs. Linde sets the tone to one of "hope."

The relationship between Mrs. Linde and Krogstad makes for a good comparison with Nora’s and Torvald’s marriage. Mrs. Linde’s and Krogstad’s decision to be together after all this time is sincere, sweet, and reasonable, even if they are choosing somewhat traditional gender roles. Although Mrs. Linde and Krogstad both suffer from significant personal and moral problems, they might have a better chance of a happy and true marriage than Nora and Torvald had. Mrs. Linde advocates revealing all to Torvald because, as her union with Krogstad suggests, she believes that it is possible to build a relationship based upon mutual dependence so long as both parties are fully aware of each other’s ideas and motives. Mrs. Linde hopes that, through her own new union, both she and Krogstad can eventually become the better people they know that they can be. This is a pattern for the “miracle of miracles,” a mutual choice to change so that both parties are truly ready for a successful marriage. Given the history of Krogstad and Mrs. Linde, however, we cannot yet see this relationship working as well as they hope. Ibsen leaves the issue open. At least the quality of respect and communication between them is already far above the situation for Torvald and Nora. In addition, all the years of thinking about each other have given Krogstad and Mrs. Linde a special anticipation for one another. This is the opposite of the effect of the years of sourness that Nora now sees when she examines her marriage.