In My Sister, the Serial Killer (2018), Oyinkan Braithwaite presents a subversive take on the crime fiction genre by reinventing the figure of the femme fatale. The femme fatale is one of the oldest and most recognisable literary archetypes. She may be defined as a mysterious woman who lures men into danger through her seductive charms. Though this archetype permeates literary and visual arts across cultures, it rose to prominence in the hardboiled detective fiction, and the Hollywood film noir of the 1940s and ‘50s. The prominent emergence of the trope at these specific periods of history might signify patriarchal anxieties about the growing shift in gender roles following the two World Wars, as women increasingly began to work in male-dominated jobs and attain sexual liberties. However, anxieties surrounding the femme fatale relate also to cultural assumptions about women. Women are believed to be naturally passive. While criminal men may provoke revulsion, their actions are seen as conforming to established patterns of masculinity. Criminal women, on the other hand, transgress not only legal law but also the social law of acceptable 'feminine' behaviour. Consequently, the femme fatales of detective fiction are duly punished or killed for their transgressions. This paper discusses how Braithwaite’s novel not only subverts the expectations associated with crime fiction but also radically challenges the usual discourses around women and crime.