Butterworth drew a long breath, eyed Mr. Gryce with some curiosity,
and then triumphantly exclaimed:

"Can you read the meaning of all that? I think I can. Don't you see that
he came expecting to find a pile of books on the table which it was
probably his business to restore to their shelves?"

"But how can he know what light is burning here? You can see for
yourself that there is no possible communication between this room and
the one in which he has always been found by any one going above."

Miss Butterworth's manner showed a hesitation that was almost naive. She
smiled, and there was apology in her smile, though none in her voice, as
she remarked with odd breaks:

"When I went upstairs--you know I went upstairs when I was here
before--I saw a little thing--a very little thing--which you doubtless
observed yourself and which may explain, though I do not know how, why
Bartow can perceive these lights from the floor above."

"I shall be very glad to hear about it, madam. I thought I had
thoroughly searched those rooms----"

"And the halls?"

"And the halls; and that nothing in them could have escaped my eyes. But
if you have a more patient vision than myself----"

"Or make it my business to look lower----"

"How?"

"To look lower; to look on the floor, say."

"On the floor?"

"The floor sometimes reveals much: shows where a person steps the
oftenest, and, therefore, where he has the most business. You must have
noticed how marred the woodwork is at the edge of the carpeting on that
little landing above."

"In the round of the staircase?"

"Yes."

Mr. Gryce did not think it worth his while to answer. Perhaps he had not
time; for leaving the valet where he was, and Miss Butterworth where she
was (only she would not be left, but followed him), he made his way
upstairs, and paused at the place she had mentioned, with a curious look
at the floor.

"You see, it has been much trodden here," she said; at which gentle
reminder of her presence he gave a start; possibly he had not heard her
behind him, and after sixty years of hard service even a detective may
be excused a slight nervousness. "Now, why should it be trodden here?
There is no apparent reason why any one should shuffle to and fro in
this corner. The stair is wide, especially here, and there is no
window----"

Mr. Gryce, whose eye had been travelling over the wall, reached over her
shoulder to one of the dozen pictures hanging at intervals from