For the three girlfriends Casey (Anya Taylor-Joy), Marcia (Jessica Sula) and Claire (Haley Lu Richardson), the shopping trip to the mall ends as a horror trip. They are made incapacitated with pepper spray and abducted. Her tormentor Kevin (James McAvoy) locks her into a cellar that surprises the frightened girls: the interior of their cellar is inviting and clean, the white beds are freshly made and a beautiful flower is ready for them on every head pillow. The girls sense hope when they hear the steps of a woman. Can she save her? This is followed by the shock: Kevin dressed up as a woman and talks with the teenagers as if he (or she) was a completely different person. Time and again, their tormentor appears to them as a different personality, which is completely unpredictable, but at the very least does nothing to them. How can the girls penetrate him and convince one of his “friendly” characters to leave them free? Time is pressing, because all of his 23 personalities speak of the “beast”, the 24th personality, which will soon break its ground and go for the girls.