"This boy took her some tea later in the afternoon," he continued, "and apparently found her in a more placid frame of mind. I returned immediately after dusk, and he reported that when last he had looked in, about half an hour earlier, she had been seated in an armchair reading a newspaper (I may mention that everything of value in the office was securely locked up!). I was determined upon a certain course by this time, and I went slowly upstairs, unlocked the door, and walked into the darkened office. I turned up the light ... the place was empty!" "Empty!" "The window was open, and the bird flown! Oh! it was not so simple a flight--as you would realize if you knew the place. The street, which the window overlooked, was bounded by a blank wall, on the opposite side, for thirty or forty yards along; and as we had been having heavy rains, it was full of glutinous mud. Furthermore, the boy whom I had left in charge had been sitting in the doorway immediately below the office window watching for my return ever since his last visit to the room above...." "She must have bribed him," I said bitterly, "or corrupted him with her infernal blandishments." "I'll swear she did not," rapped Smith decisively. "I know my man, and I'll swear she did not. There were no marks in the mud of the road to show that a ladder had been placed there; moreover, nothing of the kind could have been attempted whilst the boy was sitting in the doorway; that was evident. In short, she did not descend into the roadway and did not come out by the door...." "Was there a gallery outside the window?" "No; it was impossible to climb to right or left of the window or up on to the roof. I convinced myself of that." "But, my dear man!" I cried, "you are eliminating every natural mode of egress! Nothing remains but flight." "I am aware, Petrie, that nothing remains but flight; in other words, I have never to this day understood how she quitted the room. I only know that she did." "And then?" "I saw in this incredible escape the cunning hand of Dr. Fu-Manchu--saw it at once. Peace was ended; and I set to work along certain channels without delay. In this manner I got on the track at last, and learnt, beyond the possibility of doubt, that the Chinese doctor lived--nay! was actually on his way to Europe again!" There followed a short silence. Then-- "I suppose it's a mystery that will be cleared up some day," concluded Smith; "but to date the riddle remains intact." He glanced at the clock. "I have an appointment with Weymouth; therefore, leaving you to the task of solving this problem which thus far has defied my own efforts, I will get along." He read a query in my glance. "Oh! I shall not be late," he added; "I think I may venture out alone on this occasion without personal danger."