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.

Nevertheless, the whole affair was profoundly mysterious. As to the
change in the woman's appearance, there was little in that. The coarse,
black hair might be her own, dyed, or it might be a wig. The eyebrows
were made-up; it was a simple enough proceeding and made still more
simple by the beaded veil. But how did she come to be there at all? How
did she happen to be made-up in this fashion at this particular time?
And, above all, how came she to be provided with a lump of what I had
little doubt was poisoned sugar?

I turned over the events of the day, and the more I considered them the
less comprehensible they appeared. No one had followed the omnibus
either on foot or in a vehicle, as far as I could see; and I had kept a
careful look-out, not only at starting but for some considerable time
after. Yet, all the time, Mrs. Schallibaum must have been following.
But how? If she had known that I was intending to travel by the omnibus