The cup was yet at my lips when I chanced to look into the mirror that faced my table.  Of course it reflected the part of the shop that was behind me, including the cashier’s desk; at which the owner of the basket now stood paying for her refreshment.  Between her and me was a gas chandelier which cast its light on my back but full on her face; and her veil notwithstanding, I could see that she was looking at me steadily; was, in fact, watching me intently and with a very curious expression—­an expression of expectancy mingled with alarm.  But this was not all.  As I returned her intent look—­which I could do unobserved, since my face, reflected in the mirror, was in deep shadow—­I suddenly perceived that that steady gaze engaged her right eye only; the other eye was looking sharply towards her left shoulder.  In short, she had a divergent squint of the left eye.

I put down my cup with a thrill of amazement and a sudden surging up of suspicion and alarm.  An instant’s reflection reminded me that when she had spoken to me a few moments before, both her eyes had looked into mine without the slightest trace of a squint.  My thoughts flew back to the lump of sugar, to the unguarded milk-jug and the draught of tea that I had already swallowed; and, hardly knowing what I intended, I started to my feet and turned to confront her.  But as I rose, she snatched up her change and darted from the shop.  Through the glass door, I saw her spring on to the foot-board of a passing hansom and give the driver some direction.  I saw the man whip up his horse, and, by the time I reached the door, the cab was moving off swiftly towards Sloane Street.

I stood irresolute.  I had not paid and could not run out of the shop without making a fuss, and my hat and stick were still on the rail opposite my seat.  The woman ought to be followed, but I had no fancy for the task.  If the tea that I had swallowed was innocuous, no harm was done and I was rid of my pursuer.  So far as I was concerned, the incident was closed.  I went back to my seat, and picking up the lump of sugar which still lay on the table where I had dropped it, put it carefully in my pocket.  But my appetite for tea was satisfied for the present.  Moreover it was hardly advisable to stay in the shop lest some fresh spy should come to see how I fared.  Accordingly I obtained my check, handed it in at the cashier’s desk and took my departure.

All this time, it will be observed, I had been taking it for granted that the lady in black had followed me from Kensington to this shop; that, in fact, she was none other than Mrs. Schallibaum.  And, indeed, the circumstances had rendered the conclusion inevitable.  In the very instant when I had perceived the displacement of the left eye, complete recognition had come upon me.  When I had stood facing the woman, the brief glance at her face had conveyed to me something dimly reminiscent of which I had been but half conscious and had instantly forgotten.  But the sight of that characteristic squint had at once revived and explained it.  That the woman was Mrs. Schallibaum I now felt no doubt whatever.