Witness (1985)

A young Amish boy is sole witness to a murder; policeman John Book goes into hiding in Amish country to protect him until the trial.

If you forget the negligible crime story (and ignore the inept soundtrack by Maurice Jarre), this is a perfectly executed and well-balanced depction of a clash of cultures. 

Halliwell****: "As much about the meeting of cultures as about cops and robbers, this is one of those lucky movies which works out well on all counts and shows that there are still craftsmen lurking in Hollywood."

Maltin***: "Entertaining film is marred by jarring shifts in tone, especially toward the end."