A New York City ballet company is producing Swan Lake, and director Thomas Leroy decides to replace prima ballerina Beth MacIntyre with ballerina Nina. Nina lives with Erica, her overbearing mother and a former ballerina. Nina finds competition in new dancer Lily. Swan Lake requires a ballerina who can play the innocent White Swan, which fits Nina, and the sensual Black Swan, which fits Lily. The dancers' rivalry changes into a bizarre friendship, and Nina begins exploring a dark side of herself.