Content Warning: This section depicts recreational drug use and contains outdated and offensive language and racist stereotypes.

Sherlock Holmes, the primary protagonist, is the first and only “unofficial consulting detective,” who works with the police and private clients to solve mysteries and problems that are too difficult for others. He relies on his knowledge in a wide range of subjects from chemistry and human psychology to the forensic minutiae of tobacco ash and footprints. He requires the mental and physical stimulation of a puzzling case and falls into “dark moods” when bored. In such “dark moods,” Holmes often relies on recreational drugs. He is moody and mercurial, shifting from joyful and energetic to depressed and lethargic with little warning, often to Watson’s concern and frustration.

He devised his career as a consulting detective both to keep his mind engaged and because he possesses a deep sense of justice. Watson remarks on more than one occasion that Holmes’s brilliance would have made him a dangerous criminal if he were not so intent on serving justice. However, he is not interested in fame and recognition, usually allowing the police to take credit for the cases he solves. He believes that emotions are misleading and unnecessary and prefers to rely on rationality and logic in all things; so much so that Watson calls him an “automaton” and believes him to be unfeeling.