This essay contends that Jennifer Kent's The Babadook (2014) expands the subgenre of maternal horror by exploring reassurance as a fraught motherly act, one that is imbricated with the trauma of having to believe in the child's monsters. The film dissects the rituals that have conventionally been assigned to mothers—in this case, to single mothers—to demonstrate the precariousness of maternal authority. Maternal reassurance in particular comes to embody the terrible tension between the imperative to comfort, or, as Henry James puts it at the beginning of The Turn of the Screw (1899), “to dissipate [a child's] dread and soothe him to sleep again,” and the ineffectiveness of such verbal and gestural acts. The Babadook figures reassurance as a categorical refusal to take harm seriously, a performance of safety that does not guarantee safety at all. By linking reassurance to the mother's identity, Kent uses horror conventions to provide an unexpected critique of the burdens of maternal responsibility. What is more, she deploys these conventions to reimagine reassurance as a discourse that can powerfully generate, rather than dissipate, fear and horror and thus reconfigure the mother/son relationship in unexpected ways.