I have not had occasion to mention Shinwell Johnson in these memoirs because I have seldom drawn my cases from the latter phases of my friend’s career. During the first years of the century he became a valuable assistant. Johnson, I grieve to say, made his name first as a very dangerous villain and served two terms at Parkhurst. Finally he repented and allied himself to Holmes, acting as his agent in the huge criminal underworld of London and obtaining information which often proved to be of vital importance. Had Johnson been a “nark” of the police he would soon have been exposed, but as he dealt with cases which never came directly into the courts, his activities were never realized by his companions. With the glamour of his two convictions upon him, he had the entrée of every nightclub, doss house, and gambling-den in the town, and his quick observation and active brain made him an ideal agent for gaining information. It was to him that Sherlock Holmes now proposed to turn.