The Sign of Four is a fascinating addition to the Holmes stories, giving us fresh insights into each of the characters and their stories. Here are some key events that add layers to the series as a whole.
One key event is in the very first scene, where we find Watson observing Holmes indulging in his cocaine habit. As a doctor and a friend, Watson is concerned and disgusted by Holmes's habit, and he is distressed at Holmes's apathetic response to his attempts to cure him of it. Holmes, on the other hand, is unmoved, and he denies being actually addicted to cocaine, attributing his usage to the absence of a mentally stimulating case. This sets us up to understand both the doctor's continuing concern for his friend's health and Holmes's unusual views of his own drug usage.
Another key event is the introduction of Miss Mary Morstan, Holmes's client who eventually becomes Watson's bride. Throughout the books, Watson repeatedly falls mildly in love, but it is the gentle and pretty Mary Morstan...
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