Diagram is a simulation that responds to the rhetorical claims of two types of information systems: crime analysis software and procedurally generated games about crime. Both are systems that use algorithmic rules to identify connections between criminal suspects, in order to generate narratives about criminality. Both also implement procedures that set the scope for what qualifies as criminal, and what qualifies as an appropriate response to it. Through comparing crime analysis software to the design of procedurally generated narratives in videogame environments, the project examines both as a 'playing out' of algorithmic logic, where algorithms and interactive conventions are designed to simulate the emergence of coherent narratives about crime.