A young woman wakes up with the worst hangover of her life in a room she does not recognize. She has a difficult time moving, and as she looks around, she realizes there is a man, covered in blood, next to her. They are both naked. She assumes he raped her, because there is a green semen-like substance between her aching legs, but she cannot figure out where the blood, which she now realizes is covering her as well, would have come from with no cuts or scrapes on her body. The man wakes up and is just as confused as her. They both try to move to the bathroom to get the glass of water they can both see, but end up on the floor debilitated by the pain. They realize there are post-it notes all over the room with vague, ominous instructions and riddles telling them how to recover their strength and memory. While on the ground, the man sees her purse under the bed, and calls her over. In it they find mutilated body parts, including a severed head. A post-it note says to light a flame, so they light the candle in the room with a lighter from her purse. The head, which is glowing green, begins to speak to them in riddles, saying that they are the ones responsible for the blood and that the head was left behind by them as a guide, implying premeditation on their part. After putting the head back under the bed with no recall of what has happened to them, the man goes to the bathroom and finally drinks. The water causes an immediate shift in his body, and he crushes the glass with newfound strength, skin erupting in boils. He turns into a inhuman monster, with sharp nails, a new set of many sharp teeth, and extreme strength. He attacks the young woman, who assumes that this is the monster that attacked her, not the man who used to be in the room with her before his transformation. She eventually makes it back to the sink as he eats a human leg that is under the bed with the head. She drinks directly from the faucet, on the brink of death from his attacks, and immediately feels a shift in her body and memory. Everything comes back to her, and she remembers her and the man, in these vicious forms, going through the city causing chaos and feeding on humans. She laughs at the memory of her repulsion and fear toward the green semen, now attracted to her monstrous partner, a monster herself. They get dressed in the clothes they laid out for themselves before their bodies "regressed" to human bodies. They depart with a passionate kiss, leaving the room behind to go hunt another body to feast on, accepting that they will eventually turn back to humans, but will always seek a return to their stronger, more advanced monster forms.