¶ … solving a crime or a mystery. Attention to detail makes a detective character a great character. Sherlock Holmes, Doyle's famous character, constantly acts like the scientist who is capable of keeping his professional distance, thus keeping his objectivity, but he also leaves some tools of his detectivistic kitchen hidden from the unsuspecting eye, always ready to surprise those who think they know him pretty well. Among others, Doyle gave his character one of the best tools a detective can have: a thorough knowledge of the human nature. Sherlock Holmes is always paying attention to detail, never ignoring or dismissing little, apparently unimportant, facts, while keeping his distance and integrity. Adventure III, A Case of Identity, is a story where Holmes apparently playing with his subject, proves his genius once more, solving a mystery at the end of only one conversation with the person asking for his assistance. This short story reinforces some of Sherlock's dearest conclusions: "it is usually in unimportant matters that there is a field for the observation, and for the quick analysis of cause and effect which gives the charm to an investigation" (Doyle). Since it is made clear that the detective loves and even absolutely needs his work, the reader is able to compose a little profile of his or her own: there is a human side to Sherlock, one that takes him beyond the work of an emotionally uninvolved, very thorough professional. Sherlock never forgets that, in spite of common denominators and the importance classifications and statistics play in his line of work, human beings are unpredictable. Criminal minds, in particular, can always take one by surprise and knowing that, Holmes' strength comes...

The reader is immediately informed that the situation is far from being new. In his primary finding, Sherlock uses a term that comes from the field of medicine: symptom. He acts like a doctor who looks at his patient once and already knows what he should further look for.
Act two continues in the same manner: a second glance at his patient / client, from up close, this time, and he adds a couple important pieces to his puzzle. As the conversation continues, Sherlock's questions and the details he is encouraging his potential client to give him might seem a little off topic. Instead of letting her dive right into the problem she needs to him to solve, he is leading her to reveal her family background, her financial means, her relationships wither mother and her stepfather respectively. What it looks like a chat between friends is meant to provide him with valuable information for solving the case.

What is interesting to the reader is how he reaches his conclusions. Some of his deductions he explains to the narrator himself. For example, the fact that the woman was fidgeting on the pavement opposite his house, he explains to his interlocutor, signals that she is coming to him for something delicate, such as a love affaire. Her hesitation is therefore a symptom. Sherlock places it opposite a determined way of coming to his door, thus reaching the conclusion that her hesitation is the effect of the delicacy of the matter. He notices de tiniest detail, he picks it up, he compares…