Diagram investigates the law enforcement software Palantir Gotham as a system that uses algorithmic rules to identify connections between criminal suspects, in order to generate narratives about criminality. Through comparing this software to the design of procedurally generated narratives in videogame environments, the project examines Palantir Gotham as a 'playing out' of algorithmic logic, where algorithms and interactive conventions are designed to simulate the emergence of coherent narratives about crime. This understanding of data-driven criminal investigation as procedurally generated, in much the same way as fictional game narratives, raises considerations for algorithm regulation, explainability, and ethics.