In 1901, fingerprinting was first implemented by Scotland Yard for the purposes of criminal identification, usurping Alphonse Bertillon’s anthropometric system of body measurements in the process. Recording identity in the imprint left by a body’s digits allowed for the identification of individuals on a mass scale, ‘fixing’ their identity with apparently incontrovertible certainty. But in this chapter it will be argued that the fingerprint also served as an example of a much more enigmatic and ‘impressionistic’ identity. Gathering together the most noticeable and telling features of how fingerprints were first thought of as a means of identification, lines of comparison are then drawn with two other discourses which have a similarly impressionistic basis: firstly the early writing of Sigmund Freud and, secondly, the Literary Impressionism of Joseph Conrad. Focusing especially closely on Conrad’s Lord Jim (1900) the chapter argues that while the eponymous ‘Jim’ remains obscure even by the novel’s conclusion, the identity of the narrator, Marlow, is made apparent throughout the narration: Marlow essentially smears his prints all over the text. In lifting prints, analysing traces, and reading impressions fingerprinting, psychoanalysis and Literary Impressionism read identity in the signs made during its contact with the external world—signs which had to subsequently be enhanced, analysed and represented by authoritative experts who could make such identity visible.