Marty (played by Kristen Bell) and her boyfriend Josh have recently become distant. After several unsuccessful attempts to contact him by phone, she visits Josh, only to find his body after he has committed suicide... Marty is engulfed in guilt, haunted by visions of her boyfriend. Soon, while Marty and her friends are using an internet chat application, she suddenly receives an instant message from Josh. Marty suspects someone is using her boyfriend's computer and asks a friend to check it out, which leads to her friend encountering a terrifying experience at Josh's house... On the other hand, while Marty traces the whereabouts of the computer, she meets a young man named Dexter who bought the computer, and he discovers a series of disturbing videos on Josh's device. In the recordings, Josh narrates that he used hacking techniques to unleash terrifying entities, which he can no longer control. As Marty witnesses the suicides and erratic behavior of people around her, she increasingly senses that a cloud of terror, spread through the internet, is rapidly enveloping the entire city...