'Witness' is about a guy who is a total product of the big city - he's a tough cop, he relies on cars, phones, and guns - who hides at an Amish farm to prevent a boy (the witness) and himself from being found by the killers.
The film is less about Harrison Ford learning to live among the Amish as it is the Amish learning to live with Ford. He is a man who at first glance has no matching ideals. The film is fantastic on that level, especially thanks to Peter Weir's direction, who brilliantly shows Ford gradually becoming accepted by the Amish men.
There is very little dialogue among the characters, and Rachel (McGillis) talks even less, not because she doesn't have anything to say, but because Amish rules of life don't seem to allow her to. They are presented as a quiet people, so McGillis has the difficult task of making Rachel speak without dialogue, and she does it well, which carries over to Ford (he got an Oscar nomination, she didn't).
It's only at the climax of the film, when the action takes over that the film begins to weaken. The filmmakers seem to have some kind of answer to how the killer's storyline should be resolved, but it's not very good.
Despite the flaw, the film is excellent based on the performances of the cast, the editor who had to put all the dialogue-less scenes together (and later, won the Oscar for it), and Weir's masterful handling of the story.
