The novel, and the other "nationality" mysteries, had the unusual feature of a "Challenge to the Reader" just before the ending is revealed—the novel breaks the fourth wall and speaks directly to the reader. "I state without reservation that the reader is at this stage in the recounting of "The French Powder Mystery" fully cognizant of all the facts pertinent to the discovery of the criminal; and that a sufficiently diligent study of what has gone before should educe a clear understanding of what is to come."