after all; or if she had, her stay on the Continent must have been uncommonly short. But if she had not crossed on the boat, what was she doing in Folkestone? It was all very well to say that she had as much right to be in Folkestone as I had. That was true enough, but it was a lame conclusion and no explanation at all.
It was my custom, as I have said, to walk from my lodgings to the hospital, a distance of some five miles; but this was practicable only in fine weather. On wet days I took the tram from the "Duke of St. Alban's"; and beguiled the slow journey by reading one of my text-books and observing the manners and customs of my fellow-passengers. Such a day was the one that followed the re-appearance of Mrs. Samway. A persistent drizzle put my morning walk out of the question and sent me reluctant but resigned to seek the shelter of the tram, where having settled myself with a volume of Gould's "Surgical Diagnosis," I began to read to the accompaniment of the monotonous rhythm of the horses' hoofs and the sleepy jingle of their bells. From time to time I looked up from my book to take a glance at the other occupants of the steamy interior, and on each occasion that I did so, I caught the eye of my opposite neighbour roving over my person as it taking an inventory of my apparel. Whenever he caught my eye, he immediately looked away; but the next time I glanced up I was sure to find him once more engaged in a leisurely examination of me.
There was nothing remarkable in this. People who sit opposite in a public vehicle unconsciously regard one another, as I was doing myself; but when I had met my neighbour's eye a dozen times or more, I began to grow annoyed at his persistent inspection; and finally, shutting up my book, proceeded to retaliate in kind.
This seemed to embarrass him considerably. Avoiding my steady gaze, his eyes flitted to and fro, passing restlessly from one part of the vehicle to another; and then it was that my medical eye noted a fact that gave an intrinsic interest to the inspection. The man had what is called a nystagmus; that is, a peculiar oscillatory movement of the eyeball. As his eyes passed quickly from object to object, they did not both come to rest instantaneously, but the right eye stopped with a sort of vertical stagger as if the bearings were loose. The condition is not a very common one, and the one-sided variety is decidedly rare. It is usually associated with some defect of vision or habitual strain of the eye-muscles, as in miners' nystagmus; whence my discovery naturally led to a further survey and speculation as to the cause of the condition in the present case.
The man was obviously not a miner. His hands—with a cigarette stain, as I noticed, on the left middle finger—were much too delicate, and he had not in any way the appearance of a labourer. Then the spasm must be due to some defect of eyesight. Yet he was not near-sighted, for, as we passed a church at some distance, I saw him glance out through the doorway at the clock and compare it with his watch; and again, I noticed that he took out his watch with his left hand. Then perhaps he had a blind eye or unequal vision in the two eyes; this seemed the most likely explanation; and I had hardly proposed it to myself when the chance was given to me to verify it. Confused by my persistent examination of him, my unwilling patient suddenly produced a newspaper from his pocket and, clapping a pair of pince-nez on his nose, began to read. Those pince-nez gave me the required information, for I could see that one glass was strongly convex while the other was nearly plane.
The question of my friend's eyesight being disposed of, I began to debate the significance of that stain of the left middle finger. Was he left-handed? It did not follow, though it seemed likely; and then I found myself noting the manner in which he hold his paper, until, becoming suddenly conscious of the absurdity of the whole affair, I impatiently picked up my book and reverted to the diagnosis of renal calculus. I was becoming, I reflected disparagingly, as inquisitive as Thorndyke himself; from whom I seemed to have caught some infection that impelled me thus to concern myself with the trifling peculiarities of total strangers.
The trivial incident would probably have faded from my recollection but for another, equally trivial, which occurred a day or two later. I was returning home by way of Tottenham Court Road and had nearly reached the crossing at the north end when I suddenly remembered that I had come to the last of my note-books. The shop at which I obtained them was in Gower Street, hard by, and as the thought of the books occurred to me, I turned abruptly and, running across the road, strode quickly down a by-street that led to the shop.
As I came out into Gower Street I noticed a small, but rapidly augmenting crowd on the pavement, and, elbowing my way through, found at its centre a man lying on the ground, writhing in the convulsions of an epileptic fit. I proceeded to ward off the well-meant attentions of the usual excited bystanders, who were pulling open his hands and trying to sit him up, and had thrust the corner of a folded newspaper between his teeth to prevent him from biting his tongue when a constable arrived on the scene; upon which, as the officer bore on his sleeve the badge of the St. John's Ambulance Society, I gave him a few directions and began to back out of the crowd.
At this moment, I became aware of a pressure behind me and a suspicious fumbling, strongly suggestive of the presence of a pick-pocket. Instantly, I turned to the right about and directed a searching look at the people behind me, and especially at a bearded, nondescript person who seemed also to be backing out of the crowd. He gave me a single, quick glance as I followed him through the press and then averted his eyes; and as he did so, I noticed, with something of a start, that his right eye came to rest with a peculiar, rapid up-and-down shake. He had, in fact, a right-sided nystagmus.
The coincidence naturally struck me with some force. A nystagmus is not, as I have said, a very common condition; one-sided nystagmus is actually a rare one; and, of the one-sided instances, only some fifty per cent will affect the right eye. The coincidence was therefore quite a notable one; but had it any particular bearing? I had a half-formed inclination to follow the man; but he had not actually picked my pocket or done any other overt act, and one could hardly follow a person merely because he happened to suffer from an uncommon nervous affection.
The man was now walking up the street, briskly, but without manifest hurry; looking straight before him and swinging his stick with something of a flourish. I watched him speculatively, as I walked in the same direction, and then suddenly realized that he was carrying his stick in his left hand, and carrying it, too, with the unmistakable ease born of habit. Then he was left-handed! And here was another coincidence; not a remarkable one in itself, but, when added to the other, so singular and striking that I insensibly quickened my pace.
As my acquaintance reached the corner of the Euston Road, an omnibus stopped to put down a passenger. It was about to move on when he raised his stick, and, following it, stepped on the footboard and mounted to the roof. I was undecided what to do. Should I follow him? And, if so, to what purpose? He would certainly notice me if I did and be on his guard, so that I should probably have my trouble for nothing and possibly look like a fool into the bargain. And while I was thus standing irresolute at the corner, the omnibus rumbled away westward and decided the question for me.
I am not, as the reader may have gathered, a particularly cautious man or much given to suspicion. But recent events had made me a good deal more wary and had taught me to look with less charity on chance fellow creatures; and this left-handed person with the nystagmus occupied my thoughts to no small extent during the next day or two. Was he the man whom I had seen in the tram? Apparently not. The latter had been clean shaven and dressed neatly in the style of a clerk or ordinary City man, whereas the former wore a full beard and was shabby, almost beyond the verge of respectability. As to their respective statures, I could not judge, as I had seen the one man seated and the other standing; but, superficially, they were not at all alike, and, in all probability they were different persons.
But this conclusion was not at all inevitable. When I reflected on the matter, I saw that the resemblances and differences did not balance. The two men resembled one another in qualities that were inherent and unalterable, but they differed in qualities that were superficial and subject to change. A man cannot assume or cast off a nystagmus, but he can put on a false beard. A left-handed man may endeavour to conceal his peculiarity, but the superior deftness of the habitually used hand will make itself apparent in spite
