Dramatic irony is a literary device in which the audience possesses information that the characters do not.
In the excerpt from "A Doll's House," by Henrik Ibsen, Nora pretends to be nervous about her dance at the party so that Helmer does not read Krogstad's letter in the mailbox. A feeling of tension is developed because the letter reveals unknown information to Helmer about how Nora forged her father's signature to obtain money for her husband's health treatment in Italy.
