At one point in the story, Sherlock Holmes encounters an American lawman named Eliot Ness (who in reality was to win fame in the 1920s for his efforts to enforce the Prohibition laws). Ness does tell Holmes that this is his "first case" in which case he must have been very precocious, the story is set in 1910, while Ness was born in 1903, which would have made him seven years old at that time.