Movies like The Ninth Configuration

Sent to a converted castle in the Pacific Northwest used by the U.S. government as a psychiatric institution for military personnel who fought in the Vietnam War, the unorthodox psychiatrist, Colonel Kane, has a lot on his plate already, trying to figure out whether the inmates feign insanity or not. Still struggling with his inner demons, Kane is particularly intrigued by the psychotic former astronaut, Captain Cutshaw, whose metaphysical enquiries trigger a feverish recurring nightmare. More and more, as Kane and Cutshaw engage in intense theological debates over the existence of God and evil, the troubled scientist finds himself at a dead-end, in need of a brilliant but reckless plan to determine the root of the soldiers' complex mental breakdowns. Can Colonel Kane provide proof of an afterlife?