A mentally declining Prendergast, still employed by the Inter Ocean, writes a postcard to one of Chicago's leading defense attorneys, Alfred Trude. The content of the postcard is incomprehensible, and Prendergast does not sign his name. Trude brushes off the note and resolves it to be the work of some crackpot. However, he decides to keep the note all the same.
This chapter, albeit short, helps to position Patrick Prendergast as an important character. At this point, not much is known about Prendergast, except that he works for a newspaper, is a bit mentally ill, is obsessed with politics, and is a staunch Carter Henry Harrison supporter. With Chapter 18, Larson advances the plot a bit more without explaining how Prendergast's life might become intertwined with Burnham or Holmes.