After Martin Hewitt had rushed off to St. Augustine's Hospital with the key, the envelope, and the cypher I had brought him, I heard nothing of him till dusk fell—about six. Then I received this telegram:—

"Cypher read. Most interesting case. If you can spare an hour be outside 120 Broad Street at six thirty.—Hewitt."

I had to be at my office between eight and nine, and to keep Hewitt's appointment I should probably have to sacrifice my dinner. But I was particularly curious to know the meaning of that cypher, and just as curious to 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