Response to Pierce

"Middle Finger Mountain" is about Pierce and his girlfriend, Mary, who is terrified of dying a gruesome death. A strange man comes through their campsite without speaking, which is strange, and sets up camp. When Pierce and Mary leave with their dogs, Ellie and Jasper, someone burns all of their firewood, so they get frightened and leave camp. The strange man's dog attacks Mary, so one of the dogs attacks the man's dog. Pierce shoots the dog, then the man comes out of the shadow. Pierce levels a gun at the man, and the story ends.
I thought the plot was very engaging. The first person point of view helped with this greatly. The setting of the mountain and the topographical explanation worked nicely, and I loved the image of them camping on the middle finger of the mountain.
I would have liked more characterization. Why was Mary so afraid? What is the relationship like between these two? What made the nameless man so frightening, beyond the fact that he was sketchy? I didn't know enough about these characters to make me feel emotionally invested in the story.
On that note, I think that Mary particularly needs some insight. I'm really interested in her nightmares. Perhaps she could have one while they're camping, and she tells Pierce? That would help greatly in answering why she is so afraid of this happening.