Is the ending of Mr. Brooks (2007) an open one?

Question

The movie Mr. Brooks (2007) ends with the main character, Brooks, having a nightmare of his daughter killing him, confirming his fear of her becoming more and more like him. After which Mr. Brooks wakes up, realizing this was a nightmare, being comforted by his wife and reciting the serenity prayer.

How do we know if Mr. Brooks' nightmare was only that his daughter killed him, or he was dreaming this whole time? Is this an open ended movie, where we simply don't know? Or am I missing something and it's actually close ended, where the dream was simply the last part and not the whole action.

Reasons to consider: We know Mr. Brooks has not killed anyone in two years, and it looks like the serenity prayer is his sort of "medicine", to take in hard times of temptation. So maybe he recited the serenity prayer to stop himself, had a bad nightmare about killing again, woke up, and recited the serenity prayer again.

Answer 1

From what I can gather, you are both right and wrong! Right in feeling that the ending was open ended, but wrong in suspecting that the whole thing might have been a dream - at least, I can find no evidence to support this theory, neither in the movie itself nor from the Writer/Director (Bruce A Evans). I find it hard to believe he would not mention something as important as this aspect of the movie if it really was meant to be suggested that the whole thing was a dream.

Mr Evans) has stated in an interview on Movieweb.com that the ending was left with a few unanswered threads:

When we wrote it obviously the ending is open ended and Earl is in great pain because of his daughter. There is an open-ended... neither Earl, the daughter or Atwood has come to a conclusion.

This is due to the initial desire to make a trilogy out of the story, as further mentioned in another interview on bloody-disgusting.com

“One of the initial ideas that we weren’t able to fully incorporate into the first film [was that] Mr. Brooks was fascinated by [Detective Atwood],” Evans says. Though Demi Moore was cast as Atwood in the final film, her part was initially written for someone a bit younger, allowing Brooks to begin feeling oddly paternal toward her. “He was impressed with her. It wasn’t a love story. He saw her as the daughter that he’d always wanted. He’s tortured by his relationship with his own daughter [who ultimately reveals herself to be as murderous as her father], whereas [Atwood] represents who he had always wanted as a daughter. And that engagement would have continued on with the second film.”

The bulk of the third film would have found Brooks’ daughter Jane turning against her father and framing him for murder, setting up a battle of wills between the two as the younger Brooks tries to “get back at Daddy”.

Answer 2

I think the whole thing has to be a dream, because in the ending scene, his inner voice is asking "Why do you fight it so hard, Earl?" And the only two times that this question comes up are right at the beginning of the film and right before he kills the couple from the dance studio.

So if only the scene where his daughter kills him is a dream, why would his inner voice ask this question there? Does he have to kill someone again? So I guess he just dreamed about what could happen if he kills this couple from the dance studio and what the consequences could be. He‘s a smart killer. He has to think about everything that could happen.

I did go through a lot of sites where people discussed and speculated about the end of this movie, but no one mentioned this (for me) very important keyphrase or key question of the film, so I had to put this out there.