After an unnamed illness, the narrator sits in a coffee shop in London. Fascinated by the crowd outside the window, he considers how isolated people think they are, despite "the very denseness of the company around". He takes time to categorise the different types of people he sees. As evening falls, the narrator focuses on "a decrepit old man, some sixty-five or seventy years of age," whose face has a peculiar idiosyncrasy, and whose body "was short in stature, very thin, and apparently very feeble" wearing filthy, ragged clothes of a "beautiful texture". The narrator dashes out of the coffee shop to follow the man from afar. The man leads the narrator through bazaars and shops, buying nothing, and into a poorer part of the city, then back into "the heart of the mighty London". This chase lasts through the evening and into the next day. Finally, exhausted, the narrator stands in front of the man, who still does not notice him. The narrator concludes the man is "the type and genius of deep crime" due to his inscrutability and inability to leave the crowds of London.