William Peter Blatty directs this thriller based on his own novel. Appointed by the Pentagon to work at a remote military psychiatric hospital known as Centre Eighteen, unorthodox psychiatrist Colonel Hudson Kane (Stacy Keach) is faced with a number of patients whose mental breakdowns are seemingly unrelated to their army experiences. Chief among them is astronaut Captain Cutshaw (Scott Wilson) who believes that God is a fraud. Each of Kane's charges are tormented by inner demons, feeling their existence to be without purpose, but he begins to make progress with them all. However, as Kane's patients' condition improves his own mental state begins to deteriorate, with the line between sanity and madness becoming blurred in the process.