At Herrington High School in Ohio, it seemed that overnight, the teachers and some top students in the school became very strange. They used to be kind but now they are cold and gloomy, and this situation seems to be getting worse. Problem students Casey (Elijah Wood) and Delilah (Jordana Brewster) hid in the closet by chance, and thus witnessed the brutal murder of nurse Rosa (Salma Hayek). But not long after, Rosa appeared in front of everyone intact, but her expression was as gloomy as other teachers. Casey and others gradually realized that this series of events was related to a mysterious creature they discovered, and now this creature seems to be spreading at an unimaginable speed. The danger is approaching...