The Good Student (2006)

Ron Gibb is a widower, solitary and depressed, teaching history at an upstate New York high school. He has a small crush on Ally, a cheerleader, which is noticed by another student and the janitor. After Ally breaks up with her boyfriend, Ron drops her off at home, and a few minutes later she's kidnapped. The police are alternately suspicious of Ron and baffled because there's no ransom demand. Her father, a used car salesman, turns it into a sales event. Ron confronts Ally's dad over his business practices and offers his own reward for her return. Who has her, and why? And will Ron eventually notice a neighbor who's been trying to get his attention?