The city of the future is frequently presented as a space inscribed with ambiguities. Protagonists traversing these locations will function as formal or informal detectives, piecing together the mystery of their respective plots. But the city also invites a second detective: the reader, whose engagement with the text is akin to the cognitive process of extrapolation. Where diegetic investigations are typically character-centric, the extradiegetic mystery pertains to the nature of the fictional world itself – and only the reader is able to solve it. This chapter will analyse three texts featuring futuristic urban spaces, and the way they disperse textual and visual clues designed to lead the reader-detective towards ontological ‘truth’.