"The facts of your friend Miss Lethmere's disappearance have been communicated to us, Mr Munro," he commenced, "and we find that the lady's disappearance is much complicated by certain rather curious facts." "Well?" I asked, rather resentful that another department of the State should enter upon what, after all, was a purely personal investigation. Besides, I could see no motive. The War Office had enough to do without making inquiries regarding missing persons. "Well," said the captain politely, "I of course know you, Mr Munro, to be a well-known aviator, and have often read of the long and sensational flights undertaken by Miss Lethmere and yourself. I hope you will not think that I am personally inquisitive regarding your lady friend. But," he went on apologetically, "I am only performing my duty in inquiring in the interests of the State. You are, I know, an intensely patriotic man. I hope that I, as a British officer, am equally patriotic. Therefore we stand upon the same ground--don't we?" "Most certainly," was my reply, though, much puzzled as to the drift of his argument, I looked straight into his face, a round, rather florid countenance, with a small sandy moustache. "Good," he said. "Now I want you to answer me, in confidence, the questions I will put to you. Your replies I shall treat as absolutely secret." "Captain Pollock is from the Intelligence Department," remarked the inspector, interrupting in explanation. "I will answer, of course, to the best of my ability," I said. "But with one reservation--I will say nothing that might reflect upon a woman's honour." He pursed his lips ever so slightly. But that very slight movement did not pass me unnoticed. Was a woman's honour concerned in this? The two men exchanged glances, and in an instant a fierce resentment arose within me. Between us, upon the bare table, lay the gold chatelaine that I had bought at Bouet's, in the Gallerie at Monte Carlo a year and a half ago. It had been found in that tunnel on the main line of the Great Northern. Something tragic had occurred. Was there any further room for doubt? "The matter does not concern a woman's honour--er--not exactly so," the man in khaki said slowly. "I want to know--" And he paused, as though hesitating to explain his motive for coming along to see me. "What do you want to know about?" I asked boldly. "Come, Captain Pollock, let us face each other. There is a mystery here in Miss Lethmere's disappearance, and in the finding of this bunch of feminine fripperies in the tunnel. I intend to elucidate it." "And I will assist you, Mr Munro--if you will only be frank with me." "Frank!" I echoed. "Of course I'll be frank!" Again he looked me straight in the face with those funny, half-closed little eyes of his. Then, after a few moments' pause, he asked: "Now--tell me. Is it a fact that you, with a friend of yours named Ashton, have made some very remarkable electrical discovery?"