This essay argues that Canadian detective show Murdoch Mysteries uses the legal conflict between Canadian criminal investigation and American foreign policy to shore up an idea of Canadian national identity against an explicitly American other. First, I discuss the character of William Murdoch as a distinct departure from the literary tradition of the nineteenth-century police officer. Second, I show how Murdoch Mysteries attempts to serve as social criticism concerning socio-legal issues still relevant to Canadian society in the present day. Third, I argue that the show’s ongoing depiction of criminal jurisdictional conflict between the Toronto constabulary and Her Majesty’s government in Ottawa reveals anxieties over the present-day American threat to Canadian security and way of life. Finally, I conclude that the repeated narrative contrast between Murdoch’s scientific criminal investigations and federal strategies of American appeasement serves the secondary purpose of displacing domestic social anxieties onto an American other and reifying a Canadian national identity premised on objectivity and the rule of law.