Said Zone is guarded zealously by the government (who have not figured out how to approach it safely), which means that those who wish to take a journey to the room of wishes must hire a guide of some sort. Thus, the Stalker comes in. It is his job to break the government blockade and lead his charges across the wildness, to the building, through its mystical traps (which have killed many) and eventually to the room.
The Stalker’s clients in the story consist of a writer who seeks to renew his inspiration and a professor who wishes to achieve great fame. As the story unfolds, the strange landscape and rules which it seems to follow are a surreal backdrop which highlights the interactions between the three main characters. The whole film is very existential in nature and provokes some deep thought in the viewer once they are done.
I would have to say that Stalker is definitely one of the all-time classics of science fiction, regardless of an absence of laser guns, aliens or other high-tech trappings.