Maddie Whitaker, a sophomore at High Point University, walks across campus late at night after working in the design studio. Arriving at the Phi Mu house, she notices the front door slightly ajar, an immediate warning that something is wrong. Inside, the common room is dark and silent, shadows stretching unnaturally. Maddie discovers Lauren, a senior sister, lying motionless on the floor, a dark stain spreading across her sweater. Panicked, Maddie senses someone else is still in the house. Her fear escalates as she realizes the killer must be someone from within the sorority—someone she calls a sister.