Overall, not great. The trailer is more interesting than the movie itself. The ends didn't justify the means and I felt like the "bad guy" should have been horrendously bad to be kept in a bunker or had close familial ties which made it impossible for them to off him instead. He was neither. The father kept him in the bunker because he forced himself the mom and witnessed the dad commit vehicular mansl. on the way to his punishment. That's it.
But that's the end, let's start at the beginning. If your dad dies and leaves you a bunker and you go down there to find that he has been keeping someone prisoner, as an attorney, would you A- call the police or B- run off to find your dad's mistress because the guy in the cell just told you about her?
I'm guessing A, if you're normal. Missed opportunity. The prisoner revenge plot could have been told much better if the prisoner was freed, the family name ruined, and now, the former prisoner is coming back for revenge. Or better yet, if the prisoner was a family member (a brother or uncle) who everyone thought was dead was found and now telling the daughter the story with the intent that when he got to the punchline, he'd go after them. That's the suspense.
What we got was lackluster go betweens that could have been solved with a note from the dad saying "He forced your mom, saw me accidentally run someone over, and yeah, I've been keeping him locked up. btw, he's your real dad. Is screwed this up, fix it." Or better yet, instead of saying anything about bunker, why not absolve the issue by saying nothing and letting the man starve to death? No one knew about him anyway.
Which leads to my ultimate point. None of the story works because the premise is faulty.
This is the rich we're talking about. In real life, rich kids who drink, drive and off someone because of it, tend to get community service, rehab, and a sealed record. Same would have happened for the dad. No need to keep someone locked in an underground bunker at your family's summer home for a slap on the wrist.
I'm guessing the writers thought we wouldn't understand how rich privilege works in society, because that alone makes this story fall apart.