This chapter is built around the challenge presented by Holocaust crime fiction to the distinction between the investigator and the criminal, a defining feature of the crime genre more broadly. It discusses the importance of this binary for the narrative, ethical, and emotional impact of crime fiction, highlighting examples from classic detective fiction. After a discussion of liminal cases, where the line between investigator and criminal becomes blurred, the chapter examines the situation in historical Holocaust crime fiction, where the investigator is often linked to the Nazi regime and its crimes, creating a morally ambiguous situation. It takes as its primary case study David Thomas’ novel Ostland (2013), a novel that challenges the traditional role of the detective and questions the possibility of justice in a deeply unethical world. The chapter concludes by discussing the ethical implications and narrative techniques used in Holocaust crime fiction to portray investigators within the morally compromised context of Nazi Germany.