The One Left Behind

Four years ago, Tobias Eaton left his abusive father for Dauntless. Except, that's not all. He also left his 12 year old sister, Briana. Two years ago, Briana's only friend, Beatrice Prior, also left. She does not know where she can find Beatrice, but, she knows where to find Tobias. When it's her turn to choose, will she leave her past in Abnegation along with her father, or will she do what the test has told her, what her father trained her to do.