In which 1887 novel did Sherlock Holmes first appear?

Sherlock Holmes first appeared in the 1887 novel A Study in Scarlet.

The book introduced Holmes and Dr. John Watson, who meet in London after Watson returns from military service in Afghanistan. Stamford, an acquaintance from Watson's hospital days, brings them together because both are looking for rooms. They subsequently share rooms at 221B Baker Street.

A Study in Scarlet also establishes Holmes's analytical approach. The early plot begins with a murder in an empty house and a blood-red word written on the wall. Watson initially struggles to understand Holmes's experiments and deductions, while Holmes treats the case as an opportunity to demonstrate scientific observation.

The novel was Doyle's first published Holmes work and was followed by The Sign of the Four in 1890. It is sometimes confused with the first Holmes short story, “A Scandal in Bohemia,” which appeared later, in 1891. The title refers to the story's description of crime as a scarlet thread running through life.