The narrator, a pragmatic lawyer, becomes drawn into an investigation after a man's death is discovered in a Pullman car, and a web of circumstantial clues seems to implicate several different people. The story follows the slow unravelling of those clues through train and seaside travel, boarding-house encounters, and a series of personal accounts, including a woman’s revealing testimony. Elements of suspense, mistaken inference, and domestic detail combine as legal reasoning and chance converge to expose motives and resolve romantic and moral complications before the case reaches its unexpected conclusion.