Serious moral games offer a tool for moral development that can help players translate ‘head knowledge’ of ethical principles into habits of everyday practice. In this paper, we present the design process behind one such game: Prescott & Krueger, a serious game for training information technology students in cybersecurity ethics. Our design draws on the Four Component Model of moral intelligence and the Morality Play model for serious moral game design. We reflect on how these models influenced our design process. The Four Component Model proved a useful set of lenses for developing learning outcomes and game narrative and mechanics, however the more prescriptive Morality Play model was more difficult to apply as the development of a sophisticated ‘moral toy’ required modelling both low-level cybersecurity systems and high-level ethical interpretations. We reflect on the broader implications of this problem for serious moral game design.