A washed-up actress named Mary Dahl has become bitter and insane after falling into obscurity and suffering from a disorder that prevents her body from growing to adulthood, thus biologically cursed with literal eternal youth. She kidnaps her TV family, who all led much happier lives and more successful careers than her, and holds them prisoner on the abandoned soundstage of her old show While Robin works fast to free the actors from Baby-Doll's explosive death-trap, Batman pursues the tiny fiend through a deadly carnival funhouse.