made a rather
curious discovery. At the bottom of the tea-cup lay a single lump of
sugar. To the majority of persons it would have meant nothing. They
would have assumed that they had dropped it in and forgotten it and
would have proceeded to pour out the tea. But it happened that, at this
time, I did not take sugar in my tea; whence it followed that the lump
had not been put in by me. Assuming, therefore, that it had been
carelessly dropped in by the waitress, I turned it out on the table,
filled the cup, added the milk, and took a tentative draught to test the
temperature.

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