In theater, the conventions of realism and naturalism include set designs that create rooms that imitate those in an actual buildings. Three walls of a room will be constructed on the stage. The side of the stage that faces the audience is where the fourth wall would be. This wall is removed—in actuality, never constructed—to allow the audience to see everything that is happening onstage. This technique is part of the verisimilitude for which realism strives. The audience members are ignored by the actors, who behave as though they were carrying out real-life activities. The audience learns things about each character that is onstage, including things that other characters do not know.

In a play such as A Doll’s House, in which the plot revolves around numerous secrets, this technique helps the audience learn crucial facts from a very early point in the action. In the first scene of the play, Nora Helmer is alone onstage, and the audience can see her furtive actions as she hides small things from her husband, Torvald. These actions clue the audience in that their marriage has secrets. As the action progresses, the audience learns more secrets, such as from the private conversation that Nora has with her old friend Christine. The playwright draws in the audience and encourages them to identify with Nora as they participate in learning her secrets.