This essay analyses the serialised novel The Mysteries of St Petersburg, published in Paris in 1877–1878, and presented as an adaptation of a Russian novel by a certain Ivan Doff, "reworked and reconstructed" by two French writers, yet with no mention of their names or the original title. The genesis of the serial is plain to see in its similarity to Vsevolod Krestovsky's novel The Slums of St Petersburg, published in Russia between 1864 and 1866. Les Mystères de Saint-Pétersbourg appears to be a kind of "hypertextual" translation attempting to create a new urban mystery à la française by building on the "Mysteries of Paris' effect. It is illustrative of the different processes at work in French literature of the time, with regard to both the literary transfers and the evolution of the urban novel [roman urbain] genre. This article considers each of these aspects. It also discusses the problematical nature of hypertextual translations, which produce works which fall ambiguously between translation and rewriting.