What is the narrative significance of Holmes’ dependence on cocaine?
At the very beginning of Sign of the Four, Holmes can be found partaking of a seven percent solution of cocaine, a legal pastime at this point of history. As he explains to Watson, he makes use of this artificial stimulant when he has no problem to solve or enigma to unravel. The reader becomes aware of one Holmes’ few weaknesses: although he is the ultimate thinking machine, when presented with “idle time," his own mind becomes destructive to itself.
Should the reader feel empathy towards Jonathan Small?
After Small’s capture, the convict relays what he feels are the injustices that have been done him, along with the cruel irony of the fact that he will suffer life imprisonment for a treasure he was never able to enjoy. However, Doyle makes a point to reveal Small’s selfishness and brutality, especially in the incident of the murder of the sheik’s emissary. Also, although Small claims to regret the murder of Bartholomew, he still steals the Agra treasure and does not attempt to stop Tonga from trying to kill Holmes.
Why do both Watson and Mary rejoice at the loss of the Agra treasure?
Watson’s feelings quite obviously arise from the fact that Mary has once again returned to a position in which he, a man of meager funds, can propose marriage. Mary’s reaction reveals her considerable depth of character, as she would rather be happily married than wealthy.
Why does the story end with Sherlock Holmes once again returning to cocaine?
Holmes represents a steady and unchanging presence in the course of the Sherlock Holmes canon. Although his persona evolves somewhat over time, Doyle takes pains that no drastic changes occur to his overall character, for the purpose of maintaining Holmes’ resolute presence. For this reason, Holmes is not likely to change to any great extent from the beginning of the story to the end, even if that means retaining the same vices.
Why does Holmes allow Scotland Yard to get the credit for his cases?
He does so in order to remain unknown and continue his work in private. If this weren't the case, then criminals would know of him and make it harder for him to track them down or speak to them when on a case. It is further plausible that Holmes enjoys the activity of solving a case more than he enjoys receiving credit for the solving of it–thus his allowing Scotland Yard to take credit for the case underscores Holmes' own priorities and motives.