Girl, Interrupted's mood is defined by its uneasiness and unpredictability as it constantly jerks the reader between the highs and lows of life at McLean. One useful example comes in Chapter 8, when the hopeful news of Daisy leaving McLean and moving into a new apartment is immediately followed by the news of her suicide:
Daisy shut her eyes and paused, relishing her favorite part. “The sign.”
“What does the sign say?”
“ ‘If you lived here, you’d be home now.’ ” She clenched her hands with excitement. “See, every day people will drive past and read that sign and think, ‘Yeah, if I lived here I’d be home now,’ and I will be home. Motherfuckers.”
Daisy left early that year, to spend Christmas in her apartment.
“She’ll be back,” said Lisa. But Lisa for once was wrong.
One afternoon in May we were called to a special Hall Meeting.
“Girls,” said the head nurse, “I have some sad news.” We all leaned forward. “Daisy committed suicide yesterday.”
“Was she in her apartment?” asked Georgina.
As in this example, the narrative careens quickly between hope and despair, and mundane moments can instantly become dire. This uneasiness that permeates the book helps communicate the turbulence of being at McLean and of mental illness itself. The instability of mood in this book also trains the reader to be suspicious of everything they read, just as Susanna is suspicious of everything she experiences because the bounds between reality and illusion are blurred.