Then I suddenly stopped and ducked into a doorway. For a moment after I saw a taxicab come clattering into the avenue out of Thirty-third Street I discovered that, at her repeated gesture, it was pulling up beside the curb. I stood well back in the shadow until she had climbed into the seat, the door had slammed shut, and the driver had turned his vehicle about and started northward again. Then I skirted along the shop fronts, darted across the street, and made straight for the hotel cabstand and a taxi driver drowsily exhaling cigarette smoke up toward the tepid midnight skies. The bill I thrust into his hand took all the sleep out of his body and ended the incense to the morning stars. "Up the avenue," I said as I clambered in. "And follow that taxicab two blocks behind until it turns, and then run up on it and wait." It turned at Forty-second Street and went eastward to Lexington Avenue. Then, doubling on its tracks, it swung southward again. We let it clatter on well ahead of us. But as it turned suddenly westward, at the corner of Twenty-third Street, we broke the speed laws to draw once more up to it. Then, as we crossed Twenty-third Street, I told the driver to keep on southward toward Gramercy Square. For I had caught sight of the other taxi already drawn up at the curb half-way between Lexington and Fourth Avenues. A moment after we jolted across the car tracks I slipped away from my cab and ran back to the cross-street on foot. As I reached the corner I caught sight of a figure in a cream-colored gown cross the sidewalk and step quickly into the doorway of a shabby four-storied building. I had no time to study this building. It might have been an antiquated residence turned into a cluster of artist's studios, or a third-rate domicile of third-rate business firms. My one important discovery was that the door opened as I turned the knob and that I was able quietly and quickly to step into the dark hallway. I stood there in the gloom, listening intently. I could hear the light and hurried click of shoe heels on the bare tread-boards of the stairs. I waited and listened and carefully counted these clicks. I knew, as I did so, that the woman had climbed to the top floor. Then I heard the chink of metal, the sound of a key thrust into a lock, and then the cautious closing of a door. Then I found myself surrounded by nothing but darkness and silence again. I stood there in deep thought for a minute or two. Then I groped my way cautiously to the foot of the stairs, found the heavy old-fashioned balustrade, and slowly and silently climbed the stairway. I did not stop until I found myself on the top floor of that quiet and many-odored building. I paused there, at a standstill, peering through the darkness that surrounded me. My search was rewarded by the discovery of one thin streak of yellow light along what must have been the bottom of a closed door. Just beyond that door, I felt, my pursuit was to come to an end.