Nora lost her left arm in combat in Afghanistan. She had the choice of letting her friends die before her eyes, or loosing her arm, she chose to loose her arm.
Now she is no use to the marines. So she has to try and catch up in school which she missed. She tries to be normal but how can you when you have a missing arm?
She gets picked on at school for being different and a freak. I guess you can say that she's an undercover marine. But, someone notices her, and that person changes her life, maybe for the good or for the bad