In H. P. Lovecraft’s “The Dunwich Horror” (1929), the Whateley twins are presented as two parallel examples of monstrosity that breach the barriers between the human body and what lies in nonhuman spheres located beyond our ontological reach. They are born by a human mother, Lavinia Whateley, but their father, Yog-Sothoth, belongs to realms where the frames imposed by humanity to rationalize the world do not apply. As a result, their bodies trigger disgust when observed by human characters in the story. The contamination brought into the human world through their mere presence proves that concepts like balance and symmetry only exist from a human view. Additionally, the fact that they are twins, but not identical, reinforces the idea of the double as complementary to the self. Considering the concept of the double as a starting point, the intention of this text is to study this Lovecraft’s story as a narrative of evil twins and prove that their presence works to express the writer’s view of the universe as a context alien to human intentions and perspective. To achieve this, the Whateley twins will be analysed as dissimilar monstrous twins whose bodies make any attempt to rationalise them collapse in both characters and readers.