Describe

Child psychologist Catherine Deane (Lopez) is an expert in an experimental treatment for coma patients: a virtual reality device that allows her to enter into the minds of her patients and attempt to coax them into consciousness. When serial killer Carl Rudolph Stargher (Vincent D'Onofrio) falls into a coma before the FBI can locate his final victim, Agent Novak (Vince Vaughn) persuades Deane to enter Stargher's mind and discover the victim's location.^[1] Stargher's victim is imprisoned in a cell in the form of a glass enclosure that is slowly filling with water by means of an automatic timer.

Deane enters Stargher's twisted mind, where she is confronted by both the violent and innocent parts of the killer's psyche. The innocent half shows her the abuse he suffered at his father's hands, and the drowning of an injured bird as a mercy killing. Deane attempts to nurture the innocent side of Stargher's mind, but his murderous half thwarts her at every turn.

Despite Deane's best efforts, she becomes trapped in Stargher's dark dreamscape. Novak volunteers to enter Stargher's mind and attempts to rescue her. He breaks Deane from Stargher's hold and discovers clues to the whereabouts of his victim, Novak relates his revelations to his team and they are able to track down the location of Stargher's victim (Stargher had been entrusted by a company to take care of an advanced water pump, which he used to fill the cell with water). Novak discovers Stargher's secret underground room and saves Stargher's victim just in time. Meanwhile, Deane decides to reverse the process and pull Stargher's mind into her own. She presents Stargher's innocent side with a paradise, but his murderous side is always present, and manifests as a serpent. This time, however, Deane has all the power; she attacks the serpent-Stargher, but discovers that she cannot destroy one half without killing the other. Stargher's innocent side reminds her of the bird he drowned, and she kills him out of mercy. She adopts Stargher's dog, and successfully uses her new technique on her other coma patient.