In this paper, we illustrate a general approach to psychological inference by considering its application to a simple detective story. Detective stories provide a fertile ground for the investigation of psychological inference, because their plots so often hinge on the mental states of the characters involved. Although our analysis contains several, logically independent suggestions for h o w to tackle some of the different problems that arise in understanding the story, one guiding principle underlies our approach: the re-use thesis. According to the re-use thesis, certain inferential mechanisms whose primary function has nothing in particular to do with psychological inference cam be re-used for psychological inference tasks. In the course of the paper, w e present several examples of the re-use thesis in action. Finally, w e sketch how these applications of the re-use thesis can contribute to an understanding of our detective story.