"Arm of the Law" by Harry Harrison is a science fiction novel written in the late 1950s. The story explores the themes of law enforcement and robotics, centered around a futuristic police force on Mars where the introduction of a highly advanced police robot, named Ned, disrupts the usual course of human policing. The narrative addresses the implications of machine involvement in law and order, highlighting both the opportunities and challenges that arise when artificial intelligence intersects with law enforcement. The plot follows a lone officer in the small Martian outpost of Nineport, where he encounters Ned, the experimental police robot. Initially employed as a janitor, Ned quickly proves himself capable in active duty when a routine robbery escalates into violence, leading to his significant role in the capture of criminals, including a notorious mobster named China Joe. As the story unfolds, the protagonist grapples with the moral and practical implications of having a robot take on a police officer's role, especially as tensions rise within the criminal underbelly and leadership dynamics in Nineport shift dramatically. Ultimately, the novel raises questions about the nature of justice and the evolving role of technology in society. (This is an automatically generated summary.)