Understanding Emotional State Through Stage Directions

In dramatic literature, stage directions are essential as they provide important information about the actions and demeanor of characters, as well as details about the setting. Consider the following excerpt from a hypothetical play:

As the curtain rises, lights focus on a dimly lit room. A young woman sits at the table, her head bowed. A soft knock is heard, and she looks up sharply. Her face is a mixture of surprise and fear.

Based on this stage direction, what aspect of the play does it primarily illustrate?