Six months after deciding to get her life together and stay sober, Bridget witnesses a murder. Realizing her life is in danger and not trusting the FBI to protect her, she runs to her wealthy twin sister, Siobhan, in New York. Things start off well as the two mend their fractured relationship, but then Siobhan suddenly goes missing. Bridget assumes her sister's identity, only to discover that Siobhan's life is not as perfect as it seems, and she is no safer than before.