This is a tough one, because it started off well, then the deeper into the story we go, the more _Pet_ comes apart at the seams.
We begin with Seth, our lovable loser who reminds us that the only difference between a guy in a romantic comedy who is trying to attract a girl who's out of his league, and a creepy stalker in a horror movie, is the music.
The first act sets itself up like _Berlin Syndrome_, but has some clever twists. The movie has a fair amount of gore, but this is largely a psychological horror movie - imagine modern-day Alfred Hitchcock.
Moving on to our pet/final girl, Holly. She is thoroughly unlikeable, and the entire time I was hoping she would die, [spoiler]which is how the character needed to be played, because she's out of her fucking mind. I think discount Juno Temple did a great job, but I still wanted her to die - Holly, not Ksenia; she's probably a good person.[/spoiler]
I can honestly say that I have never seen another movie exactly like _Pet_, and the twists kept me guessing, but only until the midpoint. The closer it got to its conclusion, and more I knew I was going to be disappointed. There is another way this movie could have ended, and it is not only more plausible, but more satisfying.
Anyway, the movie looks fantastic. The acting is alright, with the highlight being Dominic's performance. I get it, a story like this has a lot of juggling to do, but if you can't stick that landing it just topples.