This dissertation examines the narrative strategies that Argentine and Brazilian authors, filmmakers, and artists have used to respond to twentieth-century dictatorships. It analyzes the appearance of horror genre conventions in novels, a film, an experimental play, an experimental artwork, and archival sources, arguing that these conventions create the sinister mood, defined as a pervasive sense of fear and apprehension in response to ominous but shadowy threats of violence and death. It argues that the texts examined in this dissertation feature the sinister mood and use familiar horror aesthetics from cross-cultural filmic and literary traditions to make political violence more legible in the cultural imaginary of dictatorship; inspire an affective response in the reader or viewer that can help them approach the experience of state terror; and ultimately resist the shadowy nature of authoritarian power. Chapter one examines esotericism, secret societies, and conspiracy, particularly the role played by Argentina’s most famous esoteric practitioner, José López Rega—known as “el Brujo”—in history and Luisa Valenzuela’s 1983 novel Cola de lagartija. It argues that, due to the shadowy, untransparent nature of Argentine politics in the 1970s, esoteric activities became conflated with behind-the-scenes political conspiracy, lending otherwise banal terror an aura of supernatural evil that exacerbated the atmosphere of fear and paranoia circulating through everyday life, literature, and culture during this era. Chapter two analyzes how the film Crónica de una fuga (dir. Israel Adrián Caetano, 2006) portrays a historical Clandestine Detention Center using the visual motifs of the Gothic haunted house to make the political dissidents’ experience of terror legible, while nevertheless highlighting the strangeness of space and time when horror lurks, detected but unacknowledged, beneath the everyday. Chapter three features another Argentine haunted house: the setting of Griselda Gambaro’s Información para extranjeros (1973), in which audiences take an unsettling tour through rooms staging scenes of uncanny violence. It demonstrates that the play evokes both the Gothic haunted house and the haunted spectacle in order to create a sinister atmosphere that exposes how authoritarian power disguises itself and relay a demand from this troubled past to intervene in our own present. Chapter four examines how Artur Barrio’s 1970 artworks featuring the Trouxas Ensanguentadas reappear the disappeared tortured bodies of Brazil’s political prisoners as abject corpses, making terror affectively known to the spectator in order to counteract the powerfully obscure nature of the sinister mood. Chapter five similarly looks at how repressive attempts to disappear bodies are turned back against the military government. Reading the contradictory materiality of Evita Perón’s embalmed cadaver in Tomás Eloy Martínez’s Santa Evita (1995) as alternately monstrous and saintly, abject and beautiful, this chapter poses that the corpse’s haunting curse reorients the sinister to hold repressors accountable for their crimes against the dead. Through its attention toward the appearance of horror genre conventions in cultural works relating to state violence and dictatorship, this intervention addresses the narrative and representative possibilities of genre, mood, and affect for portraying and contesting the legacies of state terror.