been
formally consulted, and consequently am a passive, though interested,
spectator. In the second place, I have a theory of my own which I shall
test if the occasion arises. But if you would like to take part in the
competition, I am authorized to show you the photograph and the
translation. I will pass them on to you, and I wish you joy of them."

He handed me the photograph and a sheet of paper that he had just taken
from his pocket-book, and watched me with grim amusement as I read out
the first few lines.

[Illustration: THE CIPHER.]

"Woe, city, lies, robbery, prey, noise, whip, rattling, wheel, horse,
chariot, day, darkness, gloominess, clouds, darkness, morning, mountain,
people, strong, fire, them, flame."

"It doesn't look very promising at first sight," I remarked. "What is
the Professor's theory?"

"His theory--provisionally, of course--is that the words form the
message, and the groups of letters represent mere filled-up spaces
between the words."

"But surely," I protested, "that would be a very transparent device."

Thorndyke laughed. "There is a childlike simplicity about it," said he,
"that is highly attractive--but discouraging. It is much more probable
that the words are dummies, and that the letters contain the message.
Or, again, the solution may lie in an entirely different direction. But
listen! Is that cab coming here?"

It was. It drew up opposite our chambers, and a few moments later a
brisk step ascending the stairs heralded a smart rat-tat at our door.
Flinging open the latter, I found myself confronted by a well-dressed
stranger, who, after a quick glance at me, peered inquisitively over my
shoulder into the room.

"I am relieved, Dr. Jervis," said he, "to find you and Dr. Thorndyke at
home, as I have come on somewhat urgent professional business. My name,"
he continued, entering in response to my invitation, "is Barton, but you
don't know me, though I know you both by sight. I have come to ask you
if one of you--or, better still, both--could come to-night and see my
brother."

"That," said Thorndyke, "depends on the circumstances and on the
whereabouts of your brother."

"The circumstances," said Mr. Barton, "are, in my opinion, highly
suspicious, and I will place them before you--of course, in strict
confidence."

Thorndyke nodded and indicated a chair.

"My brother," continued Mr. Barton, taking the profferred seat, "has
recently married for the second time. His age is