Although it has been a some time since I've seen this movie, it seems to have stuck quite well. The actors manage to convey quite clearly the effect the events have on them as their companions drop off one by one.
The viewer, like the main characters, never really sees what it is that has them running but whatever it is that's scaring them will have you scared as well.
The viewer, like the main characters, never really sees what it is that has them running but whatever it is that's scaring them will have you scared as well.