In which story is Mycroft Holmes first introduced?

Mycroft Holmes is first introduced in “The Adventure of the Greek Interpreter.”

The story appeared in The Strand Magazine in September 1893 and was later collected in The Memoirs of Sherlock Holmes. Watson is surprised to learn that Sherlock has an older brother, since Sherlock has rarely discussed his family or early life. Mycroft is presented as possessing extraordinary powers of observation and deduction, even surpassing Sherlock intellectually.

Unlike Sherlock, however, Mycroft lacks the energy and inclination to investigate cases actively. He spends much of his time at the Diogenes Club, a fictional London club where members are expected not to speak. The case begins when Mycroft’s neighbor, the Greek interpreter Mr. Melas, reports a disturbing incident involving a kidnapped man. “The Bruce-Partington Plans” is the other major canonical story featuring Mycroft, but it is not his first appearance.