The Adventure of the Greek Interpreter Sherlock Holmes, far from being a one-off in terms of his powers of observation and deductive reasoning, in fact has an elder brother whose skills, or so Holmes claims, outstrip even his own. As a consequence of this, Watson becomes acquainted with the Diogenes Club and his friend's brother, Mycroft. Mycroft, as Watson learns, does not have the energy of his younger brother and as a consequence is incapable of using his great skills for detective work: In spite of his inertia, the elder Holmes has often delivered the correct answer to a problem that Sherlock has brought to him.
Mycroft Holmes [...] the most indispensable man in the country." He apparently serves as a sort of human computer, as stated in "The Bruce-Partington Plans": Mycroft appears or is mentioned in four stories by Doyle: "The Greek Interpreter", "The Final Problem", "The Empty House" and "The Bruce-Partington Plans". While he does occasionally exert himself in these stories on behalf of his brother, he on the whole remains a sedentary problem-solver, providing solutions based on seemingly no evidence and trusting Sherlock to handle any of the practical details. In fact, Mycroft's own lack of practicality is a severe handicap despite his inductive talents: