Kirk was explaining how the tiny golden doll, the little charm which had been discovered after the tragedy, had been traced through the well-known jeweller in Bond Street who made it, to the Professor as purchaser; and how Greer had admitted buying it for the purpose of giving to Ethelwynn to hang upon her bracelet. But he had lost it on the previous day. Therefore it was not a clue to the assassin, as we had at first suspected. Just then the grave-eyed Antonio reopened the door, bowing, and announcing to his master that the motor-cab was at the door. Thereupon Professor Greer shook my hand, with a parting appeal to me to preserve silence. "You will, no doubt, meet your wife ere long, and she will explain much which is to you still a mystery. Remember that her devotion to you was the cause of her absence. She believed that you were in danger. That story was told her to keep her away from you, and thus draw you off the inquiry in which we feared you might be only too successful. Adieu, Mr. Holford! When I return, in a week's time, I hope you will come and have a further chat with me. In the meantime, I can only beg you to forgive me for being the unwilling means of causing you either horror, annoyance, or anxiety." And, with a hurried good-bye to the others, he turned and left the room. "A point upon which I require elucidation," I said, turning to Kirk, "is the reason why you and those other men were so inquisitive regarding the new Eckhardt tyre." "Why I called to see the tyre was simple enough," he said. "Max Leftwich was posing as the inventor of the tyre in question, and thereby trying to disguise his real profession of German secret agent. But as I had come across him in Berlin three years before in the guise of a small money-lender, I doubted his inventive genius. I came to you in order to examine the Eckhardt tyre, and I satisfied myself that Leftwich's tyre was a mere worthless imitation. My assistants also came to your garage for the same purpose, just as I predicted they would. Leftwich had opened a depot in Charing Cross Road for the sale of motor accessories, and the `improved Eckhardt tyre' was one of the inventions he claimed to be his." "But you also had a further motive?" I suggested.