The Cell (2000)

Catharine Deane is a psychotherapist who is part of a revolutionary new treatment which allows her mind to literally enter the mind of her patients. Her experience in this method takes an unexpected turn when an FBI agent comes to ask for a desperate favour. They had just tracked down a notorious serial killer, Carl Stargher, whose MO is to abduct women one at a time and place them in a secret area where they are kept for about 40 hours until they are slowly drowned. Unfortunately, the killer has fallen into an irreversible coma which means he cannot confess where he has taken his latest victim before she dies. Now, Catherine Deane must race against time to explore the twisted mind of the killer to get the information she needs, but Stargher's damaged personality poses dangers that threaten to overwhelm her.