While the relationship between modernism and its 'sister-genre' detective fiction Brian McHale, Postmodern Fiction (New York: Methuen, 1987), p. 59 has tended to be characterised in oppositional terms, recent scholarship has challenged this conceptualisation, arguing that the two forms can be productively read in relation to each other. However, the ways in which detective fiction, like modernist writing, is invested in questions of temporality remains underexplored. This paper argues that detective fiction simultaneously asserts and challenges modernity's universal, standardised time-keeping regime. This argument is developed through a detailed examination of Agatha Christie's The Murder of Roger Ackroyd, in which the criminal's ability to elude the net of modern time is only exceeded by the detective's ability to reassert it, and then through a wider discussion of the way this pattern reappears throughout the genre.