My father, Edward Royle, was head of the firm of well-known chemical manufacturers, Messrs. Royle and Shand, whose works were a feature of the river landscape close to Greenwich, and whose offices were in St. Mary Axe. He had died two years before, pre-deceasing his partner by a year. The business--a big one, for we were the largest chemical manufacturers in England--had been left solely in my hands. Shand's widow still lived with Phrida in Cromwell Road, drawing from it an income of seven thousand pounds yearly. As for myself, I was a bachelor, aged thirty-two, and if golf be a vice I was greatly addicted to it. I occupied a cosy set of chambers, half-way up Albemarle Street, and am thankful to say that in consequence of my father's business acumen, my balance at my bankers was increasing annually. At the works at Greenwich nearly two thousand hands were employed, and it had always been the firm's proud boast that they laboured under the most healthy conditions possible to secure in the manufacture of chemicals. My father, upon his deathbed, had held my hand and expressed to me his profoundest satisfaction at my engagement with the daughter of his partner, and almost with his last breath had pronounced a blessing upon our union. Yes, I loved Phrida--loved her with all my heart and all my soul. She was mine--mine for ever. Yet, as I sat at that little table in the white-enamelled restaurant gazing at her across the bowl of tulips, I felt a strange, a very curious misgiving, an extraordinary misty suspicion, for which I could not in the least account. I experienced a strange intuition of doubt and vague uncertainty. The facts we had just been discussing were, to say the least, amazing. Only the Metropolitan Police and myself were aware of the astounding discovery which had been made that morning--a discovery of which the ever-vigilant London evening newspapers had as yet no inkling. The affair was being carefully hushed up. In certain quarters--high official quarters, I believe--a flutter of excitement had been caused at noon, when it had become known that a mystery had occurred, one which at the outset New Scotland Yard had acknowledged itself utterly without a clue. About the affair there was nothing usual, nothing commonplace. The murder mysteries of London always form exciting reading, for it is surely the easiest work of the practised journalist to put forward from day to day fresh clues and exciting propositions. The present case, however, was an entirely fresh and unheard-of mystery, one such as London had never before known. In the whole annals of Scotland Yard no case presenting such unusual features had previously been reported. "Have you no theory as to what really occurred?" Phrida asked slowly, after a very long and pensive silence. "None whatever, dear," I replied. What theory could I form? Aye, what indeed?