The article analyzes the case of Luisa Nevárez, the first woman condemned to the gallows in Puerto Rico at the beginning of the twentieth century. Convicted for the killing of her almost year-old daughter, she never admitted the crime nor showed any remorse. Yet, Luisa did not make an easy transition into the sphere of the criminal. The nascent identity that was being forged in early twentieth-century Puerto Rico configured the delinquent as a masculine subject who was acknowledged as possessing intellectual malice and the capacity for social action. Luisa's condition as a woman, mother, and mulatta, her ignorance, and other factors deprived her of any possibility of entering the space of the criminal subject. Instead, the figure of Luisa oscillated between monster and madwoman in the discourses of the time. Around the mid-twentieth century her discursive figure emerges again, this time in the authorized voices of those concerned with criminal activities on the island. In this context, we find her embodying the prototype of the criminal woman: degenerate, ugly, black, and sexually insatiable. It is Luisa's abject condition that places her on the threshold of history and on the borders of the intelligible. However, the impossibility of explaining her actions in a rational way constitutes a formidable challenge for the historian. In this respect, the article is also a reflection on the limits and possibilities of the representative faculties of the historical narrative.