I had passed through two of these rooms without seeing a human being, when I came to stairs leading upward. Up these I went, several flights, until I came to a door in a ceiling. I wondered if I were still under the earth. Surely the first stairs had let into a house of some sort. I raised the door cautiously. Starlight met my eyes and I drew myself warily up and out. There I halted. A broad flat roof stretched away on all sides and beyond its rim on all sides glimmered the lights of London. Just what building I was on, I had no idea, but that it was a tall one I could tell, for I seemed to be above most of the lights I saw. Then I saw that I was not alone. Over against the shadows of the ledge that ran around the roof's edge, a great menacing form bulked in the starlight. A pair of eyes glinted at me with a light not wholly sane; the starlight glanced silver from a curving length of steel. Yar Khan the Afghan killer fronted me in the silent shadows. A fierce wild exultation surged over me. Now I could begin to pay the debt I owed Kathulos and all his hellish band! The dope fired my veins and sent waves of inhuman power and dark fury through me. A spring and I was on my feet in a silent, deathly rush. Yar Khan was a giant, taller and bulkier than I. He held a tulwar, and from the instant I saw him I knew that he was full of the dope to the use of which he was addicted--heroin. As I came in he swung his heavy weapon high in air, but ere he could strike I seized his sword wrist in an iron grip and with my free hand drove smashing blows into his midriff. Of that hideous battle, fought in silence above the sleeping city with only the stars to see, I remember little. I remember tumbling back and forth, locked in a death embrace. I remember the stiff beard rasping my flesh as his dope-fired eyes gazed wildly into mine. I remember the taste of hot blood in my mouth, the tang of fearful exultation in my soul, the onrushing and upsurging of inhuman strength and fury. God, what a sight for a human eye, had anyone looked upon that grim roof where two human leopards, dope maniacs, tore each other to pieces! I remember his arm breaking like rotten wood in my grip and the tulwar falling from his useless hand. Handicapped by a broken arm, the end was inevitable, and with one wild uproaring flood of might, I rushed him to the edge of the roof and bent him backward far out over the ledge. An instant we struggled there; then I tore loose his hold and hurled him over, and one single shriek came up as he hurtled into the darkness below. I stood upright, arms hurled up toward the stars, a terrible statue of primordial triumph. And down my breast trickled streams of blood from the long wounds left by the Afghan's frantic nails, on neck and face.