"This is very important," I said. "It is a cypher message which Mr. Hewitt can read—or I, myself, in fact, with a little time. Must you take it with you? If so, I'll make a copy now."

"Well, sir, we're responsible, you see," the man said, "so I think we must take it; so perhaps you'd better make a copy, as you suggest."

"Very well," I said, "that is done in a few seconds. You can take your man off, and I will go direct to Mr. Hewitt and Inspector Plummer with the copy." And with that I made the copy, which read thus:—

23, 19, 15, 1, 9, 14, 9, 2; 20, 8, 1,
20, 14, 14, 20, 8; 14, 5, 12, 4, 9, 7,
5, 14; 3, 8, 18, 23, 0, 14, 1, 8; 22,
9, 6, 1, 18, 3, 5, 1; 19, 14, 15, 21,
9, 0, 20, 12; 18, 12, 21, 1, 6, 23, 20,
12; 9, 18, 15, 5, 18, 13, 12, 20.

It struck me to ask the manager if the cheque just presented were one of those procured from Mr. Trenaman the night before, and I found that it was. Then I left the policemen with their prisoner and made for the nearest cab-rank. This cypher message, no doubt conveying Mayes's instructions to the man just captured, was probably of the utmost importance, and Hewitt must see it at once; and as the cab ambled along towards Barbican I busied myself in deciphering the figures according to the plan of the knight's move in chess, as Hewitt had explained to me. I could only see two noughts among the numbers, so plainly it was a longer message than the one then deciphered—one of sixty-two letters, in fact. I turned the figures into the letters corresponding in the alphabet, a for 1, b for 2, and so on, as Hewitt had done, and I arranged these letters in the squares of a roughly drawn chessboard, so that they stood thus:—

ws o a i n i b
th a t n n t h
ne l d i g e n
ch r w 0 n a h
vi f a r c e a
sn o u i 0 t l
rl u a f w t l
ir o e r m l t

The letters thus set out, to read off the message was a simple task enough, in view of the key Hewitt had given me. I began, as in the case of the Lever Key message, at the right-hand top corner, and taking the knight's move from b to e in the last square but one of the third line, thence to a at the end of the fifth line, and so to t in the seventh line, and from that to r (fifth square in bottom line), u in seventh line and so on, in the order shown by the Lever Key message, a copy of which I kept as a curiosity in my pocket-book. So I read the message through, and I set it down thus:—

Be at ruin Channel Marsh to-night twelve; wait in hall for instruc. Word final.

The general meaning of this seemed clear enough. The man whom the policeman had recognised as Broady Sims was to be at some spot—a ruined building, it would seem—in a place called Channel Marsh, at midnight, there to wait in the hall for instructions; no doubt for instructions where to take the hundred pounds he was to have got from the bank. "Word final" was not so clear, though I judged—and I think rightly—that it meant that the word "final" was to be used as a password by which the two messengers should know each other.

I was almost at my destination, and was cogitating the message and its meaning, when the cab checked at some traffic in Barbican, just by the "Compasses" public-house, and Mr. Victor Peytral hailed me and climbed on the step of the cab.