Sherlock Holmes—tall, gaunt, brilliant, and quirky—investigates crimes as a private consulting detective. His astounding ability to deduce the identities of culprits from scarce clues is known around the world, and he has closed cases involving both ordinary people and clients as high-profile as the pope. Holmes has a wide knowledge of the sciences that touch on his field; he is a master of disguise and an able student of the martial arts. He sometimes shows the impatient irascibility of the working genius, and he can be short with people—even to the point, now and then, of behaving rudely toward his friend and biographer, Dr. Watson.

Though not the first fictional detective, Holmes is among the first in a long line of brilliant, if eccentric, heroes in the crime fiction genre that his popularity helped create. His character symbolizes the newly powerful class of technical professionals, whose specialties were made possible by the rapid advances of science and engineering during the early days of the Industrial Age. His thinking represents the triumph of logic and reason over superstition. Moreover, his rapid, efficient solutions to challenging mysteries reveal the advantages of applying organized, systematic reasoning to puzzles that might otherwise be dismissed as impossible to solve.