Teddy Schoendienst is a brilliant but isolated teenager. He is bullied out of school because of his stutter and troubled by constant sexual fantasies, which he is certain will never become real. But one night, he sees a lovely young girl walk out of his closet. Her name is Elena, and she promises to fulfill all his fantasies if he will promise never to tell his little family, his father, and his beloved sister, Ellen, about her. He quickly agrees, and she fulfills her end of the bargain with apparent enthusiasm. He falls in love and walks around his house all day, saying her name under his breath. But Ellen hears him and tells him that Elena is constantly appearing in her dreams too, forcing her to do -disgusting things- with boys. Teddy reassures her that such dreams are natural at her age, but he inwardly suspects that Elena is playing a double game with his family. But before he can confront her about this, Ellen's decapitated corpse is found by the side of the river, which runs in the back of their house.

Teddy, an amateur detective, vows to discover the identities, not only of the killer but also of his strange lover. He succeeds, but what he finds is so horrible that it threatens his sanity, hili life, and even his soul.