know how it could be read; and, moreover, I knew that any
case that Hewitt called interesting would probably be interesting above
the common. So I took my hat and sought a cab.

I was first at the meeting-place--indeed, a little before my time. No.
120 Broad Street was a great new building of offices, most, if not all,
closed at this time--a fact indicated by the shutting of one of the
halves of the big front door, where a char-woman was sweeping the steps
under the board which announced that offices were to be let. I waited
nearly a quarter of an hour, and then at last a hansom stopped and
deposited Hewitt and another older gentleman before me.

"Hope we haven't kept you waiting, Brett," Hewitt said. "This is Mr.
Bell, of Kingsley, Bell and Dalton; it took me a little longer than I
expected to reach him. His offices are shut, and the clerks all gone,
but we are going to turn up the lights for a bit. The lift man is gone
too, I expect, so we shall have a good long stair-climb."

As to the lift man Hewitt was right, and during our long climb I
received, briefly, an account of the loss Mr. Bell's firm had suffered.
"I have told Mr. Bell," Hewitt said, "that it was you who happened
across the key in such an odd fashion, and when I wired I was sure he
would be glad to let you see the upshot of your strange bit of luck. I
was also pretty sure that you would like to see it, too. For I really
believe that this case--which I confess seemed pretty near hopeless a
few hours ago--is coming to an issue now, and here."

"Did you get any information out of the man in the hospital?" I asked.

"Not a scrap," Hewitt replied. "He was still insensible, and though I
saw his clothes, and they told me a good deal about the gentleman's
personal habits--which are not dazzlingly noble, to put it mildly--they
told me nothing else whatever, except that he had recently been knocked
down in the mud, which I knew already. But the cypher has told me
something, as I will explain presently."

By this time we had reached the high floor in which the offices stood,
and Mr. Bell, all wonder and pale agitation, unlocked the outer door,
and turned on the electric light.

"Now," cried Hewitt, "show me your ventilators!"

There were some, it seemed, in the top panes of the windows, but these
were not what Hewitt wanted. There were others in the form of upright
chambers or flues, made of metal, and painted the same colour as the
walls about them. They