Had Dr. Stuart sent for the Inspector? If so, I feared that the envelope was missing, or at any rate that he had detected Zara el-Khala in the act of stealing it and had determined to place the matter in the hands of the police. It was a maddening reflection. Again--I shrewdly suspected that I was not the only watcher of Dr. Stuart's house. The frequency with which the big yellow car drew up at the door a few moments after the doctor had gone out could not be due to accident. Yet I had been unable to detect the presence of this other watcher, nor had I any idea of the spot where the car remained hidden--if my theory was a correct one. Nevertheless I did not expect to see it come along whilst the Inspector remained at the house-- always supposing that Zara el-Khala had not yet succeeded. I wheeled out the "Indian" and rode to a certain tobacconist's shop at which I had sometimes purchased cigarettes. He had a telephone in a room at the rear which customers were allowed to use on payment of a fee, and a public call-box would not serve my purpose, since the operator usually announces to a subscriber the fact that a call emanated from such an office. The shop was closed, but I rang the bell at the side door and obtained permission to use the telephone upon pleading urgency. I had assiduously cultivated a natural gift for mimicry, having found it of inestimable service in the practice of my profession. It served me now. I had worked in the past with Inspector Dunbar and his subordinate Sergeant Sowerby, and I determined to trust to my memory of the latter's mode of speech. I rang up Dr. Stuart and asked for the Inspector, saying Sergeant Sowerby spoke from Scotland Yard. "Hullo!" he cried, "is that you, Sowerby?" "Yes," I replied in Sowerby's voice. "I thought I should find you there. About the body of Max.." "Eh!" said Dunbar--"what's that? Max?" I knew immediately that Paris had not yet wired, therefore I told him that Paris _had_ done so, and that the disk numbered 49685 was that of Gaston Max. He was inexpressibly shocked, deploring the rashness of Max in working alone. "Come to Scotland Yard," I said, anxious to get him away from the house. He said he would be with me in a few minutes, and I was racking my brains for some means of learning what business had taken him to Dr. Stuart when he gave me the desired information spontaneously. "Sowerby, listen," said he: "It's 'The Scorpion' case right enough! That bit of gold found on the dead man is not a cactus stem; it's a scorpion's tail!" So! they had found what I had failed to find! It must have been attached, I concluded, to some inner part of "Le Balafre's" clothing. There had been no mention of Zara el-Khala; therefore, as I rode back to my post I permitted myself to assume that she would come again, since presumably she had thus far failed. I was right.