A year after having been declared dead in the first Gulf War in 1991 Iraq only to come back to life, Jack Starks (ADRIEN BRODY) is a drifter making his way across Vermont. After helping a young girl, Jackie Price, and her drunken mother, Jean (KELLY LYNCH), get their car started, Jack accepts a ride from a stranger (BRAD RENFRO). When a cop ends up dead following a traffic stop, Jack can't remember a thing, but he's charged with the murder. Found innocent due to insanity, he ends up committed to the Alpine Grove Psychiatric Hospital under the care of Dr. Tom Becker (KRIS KRISTOFFERSON) who's oblivious to or doesn't mind that his orderlies and nurses mistreat the patients there.
Much to the concern of subordinate Dr. Beth Lorenson (JENNIFER JASON LEIGH), Becker is experimenting with a pseudo form of isolation therapy where his patients are medicated, strapped into a straight jacket and then placed for hours in an empty morgue drawer slot. In the near pitch black conditions and with the drugs doing their thing, Jack ends up hallucinating, seeing flash images of the cop's killing and other events from his past.
During what first appears to be another hallucination inside the box but then seems to turn out to be something entirely different, Jack finds himself sans the jacket and drawer, standing outside a diner. He spots a waitress (KEIRA KNIGHTLEY) who offers to give him a ride out of the cold and tries to find a place for him to stay. When that doesn't work, she allows him to stay at her place for the night, but while there, he makes a shocking discovery. His army dog tags, that he gave to young Jackie the year before, are now hanging in this woman's place.
He then realizes, but can't understand how it's possible that she's Jackie, now grown up. She doesn't believe him, stating that Jack died in 1993, some fourteen years ago. Yet, when Jack is pulled back out of the morgue slot, it's late 1992, and another inmate, Rudy Mackenzie (DANIEL CRAIG), informs him that if he doesn't resist, it's easier to make use of one's isolated time in there.
As Jack is repeatedly subjected to such "therapy," he continues to return to adult Jackie in 2007, hoping to figure out what really happened in the past, including his death that's set to occur in just a few days back in his time in the mental hospital.