To call PRISONER a horror movie is a bit of a stretch; but, without giving away any of the plot points, the movie is horrifying. I would classify PRISONER as more of a psychological-thriller, due to the taught interplay between the two main characters.
I really like character-drive plots; and, the PRISONER did not disappoint. And, while some of the flash-backs are repetitive, they do help us get to know our protagonist better than we would in a conventional telling of the tale.
The cinematography is dark and depressing; the set dressing is impressive. I thought the acting was solid; and, the music propelled the story forward without being too jarring.
If you are a fan of zombies, vampires, special effects, and gore, don't watch PRISONER. This movie is much more for slow consideration.