Ruth and Harry decide to take a romantic backpacking trip through the Pacific Northwest, but amongst the beautiful scenery, Ruth makes an unexpected discovery that sets her off on a strange, frightening new path. The couple aren't alone in the woods, and they might not be the same when they come out...if they come out.
Ruth describes her childhood in a dysfunctional family.
SPOILERS
The alien conceals itself as Ruth's boyfriend Harry. After finding out Ruth tries to kill "Harry" by kicking him and pushing him off a cliff. "Harry" comes back and tries to kill Ruth. Even though it's technically not domestic violence, this might be triggering to some.
At the beginning of the movie a deer is Stocked by something and killed. Then at 22:45 the girl walks up on the deer to find its head split in half an it’s body covered in something. It does quite a few close-ups so if you want to skip it completely skip to 24:17.
The head squashing yes, but the rest is subjective. Blood more than gore. A few characters are bisected vertically, but upon splitting they almost look like printed xrays.