There's definitely a decent story here, and pretty strong character development. It wasn't at all boring, in my opinion. The rising tension is done effectively, and we believe every decision each character makes. Also, the ending was appropriate and not overly contrived.

It did at times, however, feel like the actors were kind of *playing* at being country bumpkins with a tough start in life. That is, the acting didn't feel entirely authentic. The actress who plays Paula, for example, went way over the top with the melodrama. I was rolling my eyes at her a little by the end. I felt similar about the actor who played Noel. Just a little too much screaming and kicking when a bit more subtlety would have been much more effective.

It made me think of the movie Affliction, an indie drama from (I believe, without checking) the '90s, starring Nick Nolte and Sissy Spacek. It's the same kind of themes but much better acting. Anyway, Black Fly is a decent watch even if it's a bit forgettable.

Apparently this film is inspired by true events so that may be the reason why there aren't any crazy "twists" to speak of. The casting and pacing is good and the production value high. It doesn't really add anything new to the "redneck loses his marbles so let the massacre begin" genre but I found it entertaining despite not caring much for any of characters. The younger brother protagonist is nice enough but not much time was devoted to his backstory nor did he do that much to be super likeable IMO. He was nice enough and obviously going through tough times but I didn't feel compelled to root for him. The girlfriend was a neurotic mess who would probably jump off a cliff if told to do so. The antagonist older brother was acted out just fine but at the end of the day he was basically just another easily triggered psychopath with zero empathy. If you subscribe to a video service that includes this then ypu might want to give it a go but I wouldn't spend money to rent it. 6 stars from me.