Captain Kirk (William Shatner) and Spock (Leonard Nimoy) find that Dr. Adams has been making use of a torturous hypnosis device that can aggressively rip content out of people’s brains, leaving them in his thrall. A man named Dr. Simon van Gelder (Morgan Woodward) knew about Dr. Adams’ secret, but was unable to speak it aloud, as he has undergone brainwashing.

“Brainwashing” was a CIA cold war psyop.

The True Story of Brainwashing and How It Shaped America

“Here, then, is the brief history of brainwashing,” [Timothy] Melley writes in a 2011 paper for Grey Room. “The concept began as an [O]rientalist propaganda fiction created by the CIA to mobilize domestic support for a massive military build-up. This fiction proved so effective that the CIA’s operations directorate believed it and began a furious search for a real mind control weapon. The search resulted not in a miraculous new weapon but a program of simulated brainwashing designed as a prophylactic against enemy mistreatment. This simulation in turn became the real basis for interrogating detainees in the war on terror.”