Plagued by emotional and mental troubles, Emily (Rooney Mara) faces uncontrollable anxiety regarding her husband, Martin's (Channing Tatum) upcoming release from prison. Turning to her psychiatrist (Jude Law) for help, she is prescribed a mysterious new drug which is intended to treat anxiety and seems to work wonders...at first.

Unfortunately, the pills she takes begin causing serious, unexpected side effects that cause trouble for those around her, especially when a murder is committed.