Delphine Dayrieux is an author suffering writer's block after her latest novel becomes a bestseller. Then the mysterious Elle appears, as if summoned by magic. A beneficial friendship at first, the relationship expands into increasingly disturbing dimensions. The screenplay of the mystery drama with comedy elements was co-written by Roman Polanski and his French colleague, director and scriptwriter Olivier Assayas. The film is an adaptation of Delphine de Vigan's successful novel of the same name.