Witness

Witness is a movie starring Harrison Ford, Kelly McGillis, and Lukas Haas. When 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.
A sheltered Amish child is the sole witness of a brutal murder in a restroom at a Philadelphia train station, and he must be protected. The assignment falls to a taciturn detective who goes undercover in a Pennsylvania Dutch community. On the farm, he slowly assimilates despite his urban grit, and forges a romantic bond with the child's beautiful mother.