He had entered the tea trade not because of necessity, but because he considered it a bad thing for a man to lead an idle life. Nevertheless, the chief object of his existence had always seemed to be the unravelling of mysteries of police and crime. Surely few men, even those professional investigators at Scotland Yard, held such a record of successes. He was a born detective, with a keen scent for clues, an ingenuity that was marvellous, and a patience and endurance that were inexhaustible. At Scotland Yard the name of Ambler Jevons had for several years been synonymous with all that is clever and astute in the art of detecting crime. To be a good criminal investigator a man must be born such. He must be physically strong; he must be untiring in his search after truth; he must be able to scent a mystery as a hound does a fox, to follow up the trail with energy unflagging, and seize opportunities without hesitation; he must possess a cool presence of mind, and above all be able to calmly distinguish the facts which are of importance in the strengthening of the clue from those that are merely superfluous. All these, besides other qualities, are necessary for the successful penetration of criminal mysteries; hence it is that the average amateur, who takes up the hobby without any natural instinct, is invariably a blunderer. Ambler Jevons, blender of teas and investigator of mysteries, was lolling back in my armchair, his dreamy eyes half-closed, smoking on in silence. Myself, I was thirty-three, and I fear not much of an ornament to the medical profession. True, at Edinburgh I had taken my M.B. and C.M. with highest honours, and three years later had graduated M.D., but my friends thought a good deal more of my success than I did, for they overlooked my shortcomings and magnified my talents. I suppose it was because my father had represented a county constituency in the House of Commons, and therefore I possessed that very useful advantage which is vaguely termed family influence, that I had been appointed assistant physician at Guy's. My own practice was very small, therefore I devilled, as the lawyers would term it, for my chief, Sir Bernard Eyton, knight, the consulting physician to my hospital. Sir Bernard, whom all the smart world of London knew as the first specialist in nervous disorders, had his professional headquarters in Harley Street, but lived down at Hove, in order to avoid night work or the calls which Society made upon him. I lived a stone's-throw away from his house in Harley Street, just round the corner in Harley Place, and it was my duty to take charge of his extensive practice during his absence at night or while on holidays.