Angela Lansbury delivers an exceptionally unpleasant (and Golden Globe-winning) portrayal, demonstrating a clear departure from her usual characters, which significantly enhances this deeply unsettling thriller—one of the most intellectually stimulating films to emerge from 1960s Hollywood. Frank Sinatra and Laurence Harvey are depicted as returning from the Korean War, with Harvey receiving considerable recognition for his service, including the Medal of Honour. Both men experience distressing nightmares; when Sinatra realizes that other members of their unit share this affliction and that Harvey seems central to it all, the narrative plunges into a disturbing exploration of manipulation, psychological conditioning, mind control, and anti-communist paranoia that feels genuinely unnerving and surprisingly believable. Janet Leigh, James Gregory, and Khigh Dhiegh, portraying "Dr. Yen Lo" with palpable menace, work together effectively to craft a remarkable display of suspense and danger through skillful cinematography, understated musical cues, and consistently engaging conversations, resulting in an impressive rendition of Richard Condon's imaginative novel. It’s essential viewing.

Source on TMDB