"Look behind!" cried Smith, intense excitement expressed in his voice-- "look behind!" I turned and peered through the little square window. The cab which had stood second upon the rank was closely following us! "We are tracked!" snapped my companion. "If further evidence were necessary of the fact that our every movement is watched, here it is!" I turned to him, momentarily at a loss for words; then-- "Was this the object of our journey?" I said. "Your reference to a 'rendezvous' was presumably addressed to a hypothetical spy? "Partly," he replied. "I have a plan, as you will see in a moment." I looked again from the window in the rear of the cab. We were now passing between the House of Lords and the back of Westminster Abbey ... and fifty yards behind us the pursuing cab was crossing from Whitehall! A great excitement grew up within me, and a great curiosity respecting the identity of our pursuer. "What is the place for which we are bound, Smith?" I said rapidly. "It is a house which I chanced to notice a few days ago, and I marked it as useful for such a purpose as our present one. You will see what I mean when we arrive." On we went, following the course of the river, then turned over Vauxhall Bridge and on down Vauxhall Bridge Road into a very dreary neighborhood where gasometers formed the notable feature of the landscape. "That's the Oval just beyond," said Smith suddenly, "and--here we are." In a narrow _cul de sac_ which apparently communicated with the boundary of the famous cricket ground, the cabman pulled up. Smith jumped out and paid the fare. "Pull back to that court with the iron posts," he directed the man, "and wait there for me." Then: "Come on, Petrie!" he snapped. Side by side we entered the wooden gate of a small detached house, or more properly cottage, and passed up the tiled path towards a sort of side entrance which apparently gave access to the tiny garden. At this moment I became aware of two things; the first, that the house was an empty one, and the second, that some one--some one who had quitted the second cab (which I had heard pull up at no great distance behind us) was approaching stealthily along the dark and uninviting street, walking upon the opposite pavement and taking advantage of the shadow of a high wooden fence which skirted it for some distance. Smith pushed the gate open, and I found myself in a narrow passageway in almost complete darkness. But my friend walked confidently forward, turned the angle of the building and entered the miniature wilderness which once had been a garden. "In here, Petrie!" he whispered. He seized me by the arm, pushed open a door and thrust me forward down two stone steps into absolute darkness.