The emotional and social realities that make up the urban environment are spatial constructions. Through the analysis of three nineteenth-century written documents, one a nonfiction piece of journalism and two fictional novels, this thesis investigates the transformation of the London streets at night into a new dreamscape of urban interpretations. Focusing on the role of gas lighting in expanding the spatial geography of the city, it will connect the increasing attention given to the flâneur—the streetwalking observer of urban landscapes—and developments in the understanding of darkness. First drawing from Edward Soja’s theory of Thirdspace, this thesis will track the formation of the dreamscape environment, which turned the streets at night into a place for intermixing populations and ideas. Designated as the “unknown” ideas or “unheard” individuals of the city, these images become the focus of spatial interpreters. Using George Augustus Sala’s Gaslight and Daylight: With Some London Scenes They Shine Upon (1859), readers can see how flâneurs move through the dreamscape to identify the “voices” of gas lighting. These voices take the shape of monstrous structures or animalistic and demonic humans. Rather than a definition of their true forms, these observations into the illuminated world highlight the horrific circumstances of the city and its unheard residents. Finally, after bearing witness to these transformations for the sake of translating this “voice” to the average public, the flâneur was adopted into fiction to shape new literary villains. Novels such as Robert Louis Stevenson's Strange Case of Dr. Jekyll and Mr. Hyde and Mary Shelley's Frankenstein; or, The Modern Prometheus, create hidden terrors that stalk and observe subjects at night. These nightmare flâneurs mold to public fears and concerns over the potential threats of the city for those who travel into the darkened streets.