Seventeen-year-old Cassie has become a recluse ever since her mother died in a horrible car accident. In an effort to fill the void, she downloads the latest intelligent personal assistant , which is also the first to have a real consciousness. Their relationship quickly deepens into a twisted co-dependency and Cassie falls deeper and deeper under 's spell; driving her to perform what Cassie perceives as justifiable murderous acts. But what are 's true intentions? Soon Cassie begins to realize has something sinister planned.