Six-year-old Helen and Ellie are identical twins. But Helen is smarter, more popular and their mother's favorite, while Ellie requires special instruction at school, is friendless and is punished at every turn. Until they decide to swap places --- just for fun, and just for one day --- and Ellie refuses to switch back. The girl who used to be Helen loses her sense of self and withdraws into a spiral of behavioral problems, delinquency and mental illness. Twenty-five years later, she receives a call that threatens to pull her back into her sister's dangerous orbit. Will she take this chance to face her past?