The Ninth Configuration (1980)

An abandoned castle is the setting for William Peter Blatty's odd film. Within its walls are a group of Vietnam War-era U.S. soldiers that have been classified as crazy. A new psychiatrist arrives, tasked with finding out if they really are as mad as they appear to be and, if so, to do his best to help them.
The shrink is Stacy Keach and he's amazing in the role, the best I've ever seen him, infinitely more intriguing than many of the colourful patients.
Initially I disliked the film, but the occasional Vonnegut-esque moments kept me seated. Over time I grew more comfortable with the feverish feeling.
A pivotal scene (aprrox 45 mins into the 118 mins vers.) changed everything, thereafter a thematically darker and more theologically complex shadow was cast over all things. I believe a viewer's understanding of the second half will depend greatly on their interpretation of one particular spoken word in said scene, but the differing conclusions that result from it are equally powerful.

3½ second-hand recurrences out of 5