Sherlock Holmes, like Dobbin, relies on facts to reason and decide cases. In Signs of Four, he explained the difference between observation and reasoning in detail, and pointed out that reasoning must be based on careful observation. According to an old watch of Watson, this paper tells the living habits and personality characteristics of Watson's brother.

There is a big turning point in Signs of Four, that is, Watson and mary morstan got married.

In a word, this novel is another successful work of Conan Doyle.