Main character is an adult female, blonde, kinda young.
Basically there are murders occurring and she's seeing this guy, whom she begins to suspect whens she finds bleach in a plastic bag hidden among some hanging clothes. The guy works for the police department. Tall white guy.
There is a scene where she is with him at a fairgrounds.
Eventually, the chief of police, kinda fat black guy, decides to DNA test this dude's saliva and finds out that he's not who he says he is. The climax scene takes place in a strange factory setting. The guy reveals himself to his girl and tells her a story about how he lured a woman to him, made her drink bleach, stabbed her multiple times with a hunting knife and then shot her. That's when the chief of police shows up with a gun, the two have a struggle, and he kills the chief. Then he chases the girl up to other levels of the factory and eventually dies falling off or something.