Mattie Webber (KRISTEN BELL) is an earnest psych major at an unnamed college in an unnamed city (shot in L.A. and Bucharest, Romania). She and her best friends -- Izzie (CHRISINA MILIAN), Stone (RICK GONZALEZ), and Tim (SAMM LEVINE) -- attend classes on the "pathological mind," keep in contact by cell phone, and pirate music and movies off the internet, wholly dependent on their machines.
When Mattie's boyfriend Josh (JONATHAN TUCKER) hangs himself, Mattie at first tries to "move on," then determines to know why, as she believes she "missed the cues." Though her psychiatrist (RON RIFKIN) insists that she must face her fears and conduct "self-analysis" to become healthy, Mattie starts to believe that Josh was attacked by ghosts in the machine. At first they appear as the scary figures did in The Ring, usually appearing on computer monitors, but soon coming off the screen (Josh is attacked by a ghost in the library stacks, in a scary opening scene that sets the film's literally dark tone and throbbing soundtrack). They can soon appear via any electronic device, even with computers unplugged.
Mattie meets Dexter (IAN SOMERHALDER), who has bought Josh's computer and knows his way around a hard drive. Together, they find evidence of ghosts (victims who still live as shadows or ghosts inside "the system"), as well as the seeming cause of the attacks -- a virus they hope to fight with a counter-virus developed by Josh before he died. At the same time, Mattie's friends are killed terribly, swallowed up or dissolved, dissipating into (poorly CGI-ed) ash, and everyone else on the planet (according to brief television reports) are falling victim to the "crisis." Though most deaths occur off screen, those on screen (including Izzie and Stone) are grisly.
Eventually, Dexter and Mattie find the computer server on campus and upload the counter--virus. Still, the forces are too strong, and so the surviving humans drive off into a post-apocalyptic horizon.