Supposedly a British mystery/thriller movie from the '70s.
There is a man. He is a spy sent to some foreign place (like Istanbul). He is visiting a doctor there. The doctor gives him some drug or uses hypnosis on him multiple times. As a result, he wakes up some place that looks like a British landscape (green fields with old stones - somehow it feels like Carcosa). Maybe it isn't just the place, but another time as well.
There is a woman too, also a spy of another country. She deceives the man some way. Eventually, the man finds out.