Rhoda Penmark is a fictional character in William March's 1954 novel The Bad Seed and the stage play of the same name adapted from it by Maxwell Anderson. She is both the protagonist and antagonist of the story. Penmark is a child serial killer and psychopath who manipulates those around her. She was portrayed by Patty McCormack in the original rendition of the play and later in the 1956 film adaptation. She was also portrayed by Carrie Wells in the 1985 made-for-television adaptation In the 2018 adaptation and its sequel, she is known as Emma Grossman and portrayed by Mckenna Grace.