“Let me see,” said Holmes, standing at the corner, and glancing along the line, “I should like just to remember the order of the houses here.  It is a hobby of mine to have an exact knowledge of London.  There is Mortimer’s, the tobacconist; the little newspaper shop, the Coburg branch of the City and Suburban Bank, the Vegetarian Restaurant, and McFarlane’s carriage-building depot.  That carries us right on to the other block.  And now, doctor, we’ve done our work, so it’s time we had some play.  A sandwich and a cup of coffee, and then off to violin-land, where all is sweetness, and delicacy, and harmony, and there are no red-headed clients to vex us with their conundrums.”

My friend was an enthusiastic musician, being himself not only a very capable performer, but a composer of no ordinary merit.  All the afternoon he sat in the stalls wrapped in the most perfect happiness, gently waving his long thin fingers in time to the music, while his gently smiling face and his languid, dreamy eyes were as unlike those of Holmes the sleuth-hound, Holmes the relentless, keen-witted, ready-handed criminal agent, as it was possible to conceive.  In his singular character the dual nature alternately asserted itself, and his extreme exactness and astuteness represented, as I have often thought, the reaction against the poetic and contemplative mood which occasionally predominated in him.  The swing of his nature took him from extreme languor to devouring energy; and, as I knew well, he was never so truly formidable as when, for days on end, he had been lounging in his armchair amid his improvisations and his black-letter editions.  Then it was that the lust of the chase would suddenly come upon him, and that his brilliant reasoning power would rise to the level of intuition, until those who were unacquainted with his methods would look askance at him as on a man whose knowledge was not that of other mortals.  When I saw him that afternoon so enwrapped in the music at St. James’s Hall, I felt that an evil time might be coming upon those whom he had set himself to hunt down.

“You want to go home, no doubt, doctor,” he remarked, as we emerged.

“Yes, it would be as well.”

“And I have some business to do which will take some hours.  This business at Saxe-Coburg Square is serious.”

“Why serious?”

“A considerable crime is in contemplation.  I have every reason to believe that we shall be in time to stop it.  But to-day being Saturday rather complicates matters.  I shall want your help to-night.”

“At what time?”

“Ten will be early enough.”

“I shall be at Baker Street at ten.”

“Very well.  And, I say, doctor! there may be some little danger, so kindly put your army revolver in your pocket.”  He waved his hand, turned on his heel, and disappeared in an instant among the crowd.