We took our positions and waited. I felt pretty sure that if Mayes sent at all it would be early, for obvious reasons. And I was right, for the very first customer was our man.
He stepped in briskly scarcely a minute after the manager had ceased speaking, and I remembered having seen him waiting at the street corner as I came along. He was a well-dressed, smart enough looking man, in frock coat and tall hat. He took a letter-case from his pocket, picked out a cheque from the rest of the papers in it, and passed it under the wire grille of the counter.
The cashier took it, turned it over, and shifted mechanically to post the amount in the book on his desk. As he did so his elbow touched the heavy ledger which the manager had pointed out to us, and it fell with a crash. The cashier calmly put his pen behind his ear, and stooped to pick up the book, but even as he did it the two Scotland Yard men were out before the counter, and had sidled up to the stranger, one on each side.
"May we see that cheque, if you please?" asked one, and the cashier turned its face toward him. "Ah, just so; a hundred pounds—Mayes. We must just trouble you to come with us, if you please. There is some explanation wanted about that cheque."
I had followed the two men from the manager's room, and now I saw that while one had laid his hand on the stranger's shoulder the other had taken him by the opposite arm. "Why," said the former, looking into his face, "it's Broady Sims!"
"All right," the man growled resignedly. "It's a cop. I'll go quiet."
But as he spoke I saw the free hand steal out behind him and pitch away a crumpled fragment of paper. One of the policemen saw it too, followed it with his eyes, and saw me snatch it up.
"That's right, sir," he said, "take care of that; and we'll have a cab, in case anything else drops accidentally. It's just a turning over, Broady, that's what it is."
I spread out the piece of paper, and was astonished to find inscribed on it just such another series of figures, in groups of eight, as was found in the cypher message in the Case of the Lever Key.
Here was a great find—a secret message as clear to me as to Mayes himself, and as likely as not the scrap of paper that would hang him! I took one of the plain-clothes men aside while the other kept his hold of Broady Sims.