she might have gone to meet it and entered before I did. But she could
not have known: and moreover she did not meet the omnibus, for we
watched its approach from some considerable distance. I considered
whether she might not have been concealed in the house and overheard me
mention my destination to Thorndyke. But this failed to explain the
mystery, since I had mentioned no address beyond "Kensington." I had,
indeed, mentioned the name of Mrs. Hornby, but the supposition that my
friends might be known by name to Mrs. Schallibaum, or even that she
might have looked the name up in the directory, presented a probability
too remote to be worth entertaining.

But, if I reached no satisfactory conclusion, my cogitations had one
useful effect; they occupied my mind to the exclusion of that
unfortunate draught of tea. Not that I had been seriously uneasy after
the first shock. The quantity that I had swallowed was not large--the
tea being hotter than I cared for--and I remembered that, when I had
thrown out the lump of sugar, I had turned the cup upside down on the
table; so there could have been nothing solid left in it. And the lump
of sugar was in itself reassuring, for it certainly would not have been
used in conjunction with any less conspicuous but more incriminating
form of poison. That lump of sugar was now in my pocket, reserved for
careful examination at my leisure; and I reflected with a faint grin
that it would be a little disconcerting if it should turn out to
contain nothing but sugar after all.

On leaving the tea-shop, I walked up Sloane Street with the intention of
doing what I ought to have done earlier in the day. I was going to make
perfectly sure that no spy was dogging my footsteps. But for my
ridiculous confidence I could have done so quite easily before going to
Endsley Gardens; and now, made wiser by a startling experience, I