This might be a movie or an episode from a TV show, I'm not sure.
My guess would be 70's, but might be early 80's.
I remember the main plot is around a village in a paradesic garden. Every so often, a "sacrifice" must be made, in which one or two people are sent through a mysterious cave. This turns out to be a corridor with decontamination (he flies from one end to the other?). After that, the main protagonist finds out he is actually in a spaceship and the current pilots are dead.