Night Moves (1975)

Harry Moseby runs away from his crumbling marriage by chasing a runaway teenager, mistaking petty sleuthing for moral clarity. His stubborn refusal to step back when the case turns poisonous pulls innocent bystanders into a smuggling racket that leaves a trail of corpses across the Florida Keys. The final, circling boat adrift over murky waters serves as the ultimate metaphor for a detective who ruined everything he touched.