Both Stevenson’s The Strange Case of Dr Jekyll and Mr Hyde (1886) and Clarke’s ‘The Mystery of Major Molineux’ (1881) appear to have influenced a small group of Australian short story writers who were working in the decade immediately preceding Federation. Their work appeared in The Bulletin, The Boomerang and the Australian Journal, as well as in privately edited collections of short fiction. This essay examines Campbell McKellar's 'The Premier's Secret' (1887) and Ernst Favenc's 'My Only Murder' (1893), in addition to Clarke’s ‘The Mystery of Major Molineux’, to determine how these three writers used the concepts of degeneration, the double brain and multiple personality, and to what ends. My contention is that, like Stevenson, the colonial writers explore atavism and reversion by using motifs and elements drawn from Gothic and popular crime fiction to expose the depravity of members of the nation’s ruling classes, but paradoxically also to lend them a more human face. While we might recognise greater moral ambiguity in the Australian stories compared to Stevenson’s, accounting for that ambiguity is more difficult. One possible explanation is that the writers were not just more mindful of the public’s growing taste for fictions that shocked and thrilled, they were also more willing to satisfy this demand. A second is the greater class mobility within Australian society compared to that of Britain, and that this generated a stronger tolerance for the savage impulses that lay at the heart of the settler enterprise. In other words, in that the violence that accompanied settlement had become a part of everyday life, the Australian stories appear to be more at ease with the atavistic elements of their characters – the veneer of civilisation seems to be much thinner in Australia than in Britain. Closely related to this idea is Australian audiences’ more ready acceptance of personal traits like eccentricity, mateship and anti-authoritarianism, which can arguably be traced to the colony’s convict beginnings but also to its mounting desire for an independent future.