The story structure was very solid and the pacing was good. I felt connected with he characters, which is impressive given the short length of the story. The dialogue was good, although it got a little choppy a couple of time and lagged, but overall it was engaging. The concept for the story was excellent. It wasn't the same old tired monster in the forest story. Given the setting, it was natural to think it would be well tread material, but the fact that the story had the ending twist made the story that much more pleasing. I wanted to read more which I think, in a general sense, is really what the point is.
There were a few things that jumped out at me as holes in the plot and/or just seemed odd. The first one is a little thing, but when the mother denies the daughter a drink, she calls her mom "corny". That word is jarringly out of place. I think what the writer was trying for was something like "uptight" or "prudish". Second, I don't understand if, we are to believe that the brother saw the beast, how is in fact the beast. Was he possessed? I'm just not sure how he sees the beast, seems legit scared and then IS the beast. I think I can safely assume, based on the quality fo the writing, that the writer was attempting to communicate how that is possible, but I personally didn't get it. Third, there isn't any way the son would stay outside when his mom gives him the option of going inside with her. Just didn't make any sense. If, hypothetically he was stalling to be alone with his sister to eat her guts out, its not clear why that makes sense. The writer makes is clear that the boy is frightened. If the writer was attempting to get accross that the boy's fear was not genuine, I don't think hat was effectively communicated.
The concept is excellent, the writing is really solid, the plot and pacing is good, and I think will some tying together, the script could be excellent.