Sir Arthur Conan Doyle, in his second adventure of Sherlock Holmes, uses a similar literary device as in the first novel. A mystery is presented by a distressed lady, a crime is committed, Sherlock and Dr. Watson come hot on the trail, Sherlock figures it all out pretty quickly, the perpetrator is caught, and then Old Peg Leg, a convict and accomplice to a murder, tells all. In both novels, the confession of the felon brings one to have compassion for the killer and an understanding for why the crime was committed. There was an injustice and things were made right by taking the situation into one's own hand and creating a just ending to a sad story.
This story involves south sea islands, penal colonies, double crosses, jewels, and in a round about way, a love interest which results in a fiancé for Dr. Watson. It also reveals the cocaine addiction that Sherlock has. It seems that when he is not using his vast brain power solving a complicated crime, he gets extremely bored and needs the stimulation that he finds in coke. I assume that in that day, this was not as frowned upon as it is today.
As for the story and the writing, I was not as taken with this narrative as I was with The Scarlet Thread. Sherlock allows the inept police officials to take the credit for solving the crime and apprehending the criminals, as he did in the first novel. So how then does he get his famous reputation and how does he earn a living? I hope these questions will be answered in future stories.