Devon is always being left behind by her genius twin sister, Drew. At this point, it's a fact of life. But Devon has one last plan before Drew leaves for college a whole year early: the Best Summer Ever. After committing to the bit a little too much, though, the twins and their chaotic circle of friends learn why you don't ever mess with a Ouija board if you actually want to survive the best summer ever, and they soon find themselves being hunted down by... a demon? But while there's no mistaking that the creeping, venomous figure is not from around here, its murderous method doesn't feel very demonic at all. In fact, it's downright human--going after them in typical slash-movie kill order. And that means Devon, the blonde, is up first, and her decade-long crush, Yaya--pretty, brunette, virginal Yaya--is the Final Girl, who must kill or be killed to end the cycle. Devon has never liked playing by anyone else's rules, not even a demon's, and the longer this goes on, the more she feels Drew and Yaya slipping away from her even as she tries to help them all survive. Can they use their horror movie knowledge to flip the script and become the hunters instead of the hunted? Or will their best summer ever be their last...?