A Dark Place (2018)

Donald is a slow-witted sanitation worker in a small town with his loyal mother Betty. He has a daughter with a woman named Linda who he had an affair with once, and he is convinced himself he and her and the daughter are going to be a family. His loyal co-worker Donna actually cares about him much more than Linda.

One day a boy is found drowned in the woods and Donald's convinced it wasn't a drowning and since no one else seems to care he begins to investigate the death of the boy. He even questions the boys young friends, posing as a grief counselor. Several people want him to back off. He even comes under suspicion. One night some masked men hold him at gunpoint and try to make him leap off a bridge before Donna shows up with a gun and saves him. Seem to give up. And when the sheriff gives him a ride one night and threatens him, he is ready to give up, but now Donna believes the boy didn't drown by accident and gives him a tip which leads him to pediatrician Joel, who claims nothing happened, but Donald finds evidence leads him to confront the boy's mother. He tells her he knows Joel molested the boy, with help from his friend the sheriff. The boys mother tearfully claims she didn't know what was happening and she left the boy with Joel because she had to work. Donald says he thinks she just didn't want to know that it was happening. Donald gets an arrow gun, chases Joel around his farm, and kills him. The police, led by the stunned sheriff show up and arrest Donald. It is implied Donald will go to prison, and no one will ever find out the sheriff knew boy was being molested.