"Without a doubt. Go down to Hounslow to-morrow and discover what you can regarding these friends of hers, the Chetwodes, and their associates. In inquiries of this sort you must carefully work back." Now, I had for years rather prided myself upon my shrewdness. I had often set myself the task of clearing up those little unimportant mysteries of life which occur to every man; and more than once, while at the hospital, I had rendered service to the police in their inquiries. That same afternoon, while Bob was out visiting his patients, I chanced to put my hand in the ticket-pocket of my frock-coat, and felt something there. The coat was the one I had worn when called out to become the husband of Feo Ashwicke, and from the pocket I drew a half-smoked cigarette. I am not in the habit of placing cigarette ends in my pockets, and could not, at first, account for its presence there; but, on examination, I saw that it was the remains of one of an unusual brand, for upon the paper were tiny letters in Greek printed in blue ink. A second's reflection, however, decided me: it was the cigarette which the Major had given me. It had gone out while I had been speaking, and with it in my hand I had rushed upstairs to my wife's room, and instead of casting it away had, I suppose, thrust it into my pocket, where it had remained unheeded until that moment. I examined it with the utmost care and great interest. Then I descended to Bob's little dispensary, at the back of the house, and, finding a microscope, took out some of the tobacco and placed it beneath the lens. Tiny but distinct crystals were revealed clinging to the finely-cut tobacco, crystals of some subtle poison which, dissolved by the saliva while in the act of smoking, entered the system. The cigarette had narrowly proved fatal to me. At once I lit the spirit-lamp, cleaned and dried some test-tubes, and set busily to work to make solutions with the object of discovering the drug. But although I worked diligently the whole afternoon, and Bob, on returning, assisted me, we were unable to determine exactly what it was. The remainder of the cigarette, including the paper bearing the mark of manufacture, I carefully preserved, and on the following morning went down to Hounslow to ascertain what I could regarding my unconscious wife. Bob remained at Rowan Road to look after his patients, but declared his intention of relieving me if any watching were required. Therefore, I went forth eager to ascertain some fact that would lead me to a knowledge of the truth. Hounslow, although but a dozen miles from Charing Cross, was, I found, a dull, struggling place, the dismal quiet of which was only relieved by a few boisterous militiamen in its long street. I took up my quarters at the historic _Red Lion_, and over a whisky-and-soda made inquiries of the plethoric landlord as to the whereabouts of Whitton. It lay beyond the town, half-way towards Twickenham, he told me.