Wilkie Collins’s Armadale is compared with his short story ‘Mad Monkton’, both of which speculate about negative hereditary transmission. Whereas ‘Mad Monkton’ portrays the consequences of hereditary insanity as devastating and inescapable,Armadale engages with a broader range of hereditary threats, but does not depict them as insurmountable. I attribute this change to both Collins’s choice of genre and his growing sense of responsibility as a widely read author. As a sensation author Collins had an eye for the alarming, and in Armadale his imaginative speculations foreshadow the paranoia of developing degenerationist thought which expressed concern with numerous issues, including the hereditary nature of criminality and insanity, atavism, regression, miscegenation, and acquired characteristics which could develop into morbid traits in the next generation. By associating different types of degeneration with different characters, and by offering different reasons for the development of that degeneration, Collins raises questions about class and race. However, Collins crucially opposes the view that morality is irrevocably hereditary at the same time as he invokes the fearful consequences of if it were. Moreover, Collins attempts to create sympathy with, rather than to reject or isolate, social outsiders.