Child psychologist Catherine Deane (Jennifer Lopez) is an expert in an experimental treatment for coma patients: a virtual reality device created by Dr. Henry West (Dylan Baker) that allows her to enter the minds of individuals in a vegetative state and attempt to coax them into consciousness. Her current patient, a boy named Edward (Colton James), seems to be making progress during her sessions with him, but there's no outward sign of improvement in his condition and his parents are beginning to wonder whether Catherine's conversations with Edward might simply be drug-fueled delusions.Far from the research facility, in an underground lair, serial killer Carl Rudolph Stargher (Vincent D'Onofrio) performs the post-mortem ritual on his latest victim. Stargher captures young women, psychologically tortures and drowns them, and then bleaches their corpses completely white. Finally, he clamps a collar around the corpse's neck, making it his possession, a macabre type of doll.Stargher is in the process of stalking and kidnaping his next victim, a woman named Julia Hickson (Tara Subkoff) when the police work of detectives Peter Novak (Vince Vaughn) and Gordon Ramsey (Jake Weber) finally yields a break in the case. The authorities learn the identity of the killer and surround his home. Just before they can finally make the arrest, Stargher suffers a seizure and slips into a coma. Doctors diagnose Stargher with a rare neurological disease that renders his condition irreversible.Meanwhile, Julia wakes up to find herself imprisoned in Stargher's specially designed glass enclosure that is slowly filling with water by means of an automatic timer. It's up to Catherine and Dr. West's team to access the mind of Stargher and persuade him to reveal the location of Julia Hickson in time to save her life. Otherwise, in less than 48 hours, the tank will fill with water and she will drown.Catherine enters Stargher's twisted mind, where she is confronted by the killer's fractured psyche. The boy Carl is too scared to talk, while the adult Stargher rules his inner world like an evil overlord. Another adult version of Carl explains to Catherine that his father abused him and shows her how he began his practice of killing women. Catherine attempts to nurture the innocent side of Stargher's mind, but his murderous half thwarts her at every turn. Eventually the evil Stargher takes control, attacks Catherine and enslaves her mind. Catherine becomes trapped in Stargher's dark dreamscape.Novak volunteers to enter Stargher's mind and attempts to rescue her. He, too is captured by Stargher, but fortunately he manages to remind Catherine that shes dreaming, which breaks her from Stargher's hold. She overpowers Stargher so that they can make an escape. Catherine doesn't manage to get Carl to talk before both she and Peter awaken from the session, but Peter is able to remember a symbol he saw within the dream, a trademark associated with a specialized piece of equipment that leads them to the isolated area where Stargher has built his secret underground room. Novak finds Hickson just in time to save her life.Meanwhile, Catherine decides to reverse the mind link process and pull Stargher's mind into her own to see if she can heal the innocent part of his self. She presents his inner child, Carl, with a paradise, but his murderous side is always present, and manifests as a serpent. This time, however, Catherine has all the power; she attacks the serpent-Stargher, mortally wounding him. Unfortunately, she learns that the two personalities are inextricably linked and the inner child is also dying. Because Stargher's personal mythology equates drowning with being "saved," in the baptismal sense, he dies serenely in the beautiful dream world Catherine created in her mind, his soul finding peace at last as she drowns him in a sparkling pool of water.The use of Dr. West's technology to help the police locate Julia Hickson has given his work new credibility, and Catherine is able to use the reversal technique to bring Edward into her mind, where he will hopefully make new strides with his therapy.