The film is a domestic horror thriller telling of a family's destruction by the introduction of a sexually predatory femme fatale into the household. A piano composer has just moved into a two-story house with his wife and two children. When his pregnant wife becomes exhausted from working at a sewing machine to support the family, the composer hires a housemaid to help with the work around the house. The new housemaid behaves strangely, catching rats with her hands, spying on the composer, seducing him and eventually becoming pregnant by him...