Let me start off by saying that the reviewer who speaks of "the happy ending" is simply talking about the setup to the movie, that the man character visits a massage parlor that provides additional services.
Neil, our main character, is sent to the massage parlor as a joke by his mean spirited co-workers. Upon finding this out, he attempts to choke one of them. He winds up going back to the massage parlor, only to thwart a robbery that results in the death of the would-be robbers who are shot by Perla, who was servicing Neil. The two go on the run together, and see to be hitting it off. Perla relates that the robbers were somehow involved with her bosses, and that her life is now in danger. They talk of heading for Mexico when their care breaks down. They then enjoy a beautiful walk into town, and meet a nice, friendly mechanic who takes them home to stay with his family for the night...which turns out to be an interesting group of folks.
At this point, instead of continuing in a positive direction, well, Neil's issues catch up with him...and the movie goes down hill fast.
I've already warned that this post has spoilers, but here it is again. I guess I understand that Neil's jealousy and insecurities would real their ugly head, and he would turn on Perla, but the ending was simply too "quick" and out of nowhere. It's not really clear who killed Perla and kills Neil - was it the "bad guy" who was following them? One of the cops? If so, there's a huge plot hole on how they knew where to find them.
I ranked this movie a six, but it should probably be like a 5.3 because I thought up until the very end, it was pretty good.....but the ending took at least a point away.