In late 90's L.A., Hannon Fuller runs a major computer company. He also created a VR replica of 1937 L.A. Fuller is killed as beta testing begins, with Fuller's friend and mentoree, Douglas Hall, as the prime suspect. Evidence against Hall is so overwhelming that even he thinks he's at fault. Between interrogations from Detective Larry McBain, Hall encounters Jane Fuller, Hannon's estranged daughter, currently occupied with shutting down the VR equipment. Hall romances Jane, taking her to a bar. There, a bartender claims to have seen Hall and Fuller meet on the night of the murder. Hall is arrested; Jane later provides him with an alibi, releasing him from imprisonment.
With help from associate Whitney, Hall finds a message within 1937. Upon entering, Hall becomes "John Ferguson." There, he learns a "Jerry Ashton" learned his true nature after reading Fuller's message. Ashton nearly kills Hall, with Hall barely escaping VR.
Unable to find Jane, Hall meets her double, but she doesn't recognize him. Hall decides to drive where he would never otherwise drive and discovers a place that is only a wireframe. Hall has an epiphany, 1990's L.A. is a fabrication as well. Indeed, 1990 is a single VR amongst thousands, yet only his created VR technology. Jane is real, only entering 1990 to control Fuller's company and shut down 1937. Hall is modeled after Jane's spouse, David. David is the true killer, using Hall's body, when Jane fell for the virtual Hall.
Whitney enters 1937 as Jerry Ashton, whom kidnapped John Ferguson. Jerry dies in a car crash, sending Ashton's mind into Whitney's body. David manipulates Hall to kill Ashton, who then tries to assault Jane. Jane is saved by Detective McBain, who shoots David, asking Jane to leave them "down here." Hall's mind moves to David's body, waking in 2024. He reconnects with Jane and her father, Hannon Fuller. As Jane explains about the simulation, the film ends with a black out akin to a PC screen.