your murderer picked up a cab. It's perfectly
clear. No one has touched that pistol since the man who used it threw it
from the window of Number Seven."

"You mean Number Six," corrected Gritz.

"I mean Number Seven. We know where the murderer took a cab, now we'll see
where he left the hotel." And hurrying toward his dog, he called: "Back,
Caesar!"

Obediently the dog trotted back along the trail, recrossing the street
where he had crossed it before, and presently reaching the point where he
had first caught the scent. Here he stopped, waiting for orders, eying M.
Paul with almost speaking intelligence.

"A wonderful dog," admired Gritz. "What kind is he?"

"Belgian shepherd dog," answered Coquenil. "He cost me five hundred francs,
and I wouldn't sell him for--well, I wouldn't sell him." He bent over and
fondled the panting animal. "We wouldn't sell our best friend, would we,
Caesar?"

Evidently Caesar did not think this the moment for sentiment; he growled
impatiently, straining toward the scent.

"He knows there's work to be done and he's right." Then quickly he gave the
word again and once more Caesar was away, darting back along the sidewalk
_toward_ the Champs Elysees, moving nearer and nearer to the houses and
presently stopping at a gateway, against which he pressed and whined. It
was a gateway in the wall surrounding the Ansonia Hotel.

"The man came out here," declared Coquenil, and, unlatching the gate, he
looked inside, the dog pushing after him.

"Down Caesar!" ordered M. Paul, and unwillingly the ardent creature
crouched at his feet.

The wall surrounding the Ansonia was of polished granite about six feet
high, and between this wall and the hotel itself was a space of equal width
planted with slim fir trees that stood out in decorative dignity against
the gray stone.

"This is what you call the alleyway?" questioned Coquenil.

"Exactly."

From the pocket of his coat the detective drew a small electric lantern,
the one that had served him so well earlier in the evening, and, touching a
switch, he threw upon the ground a strong white ray; whereupon a confusion
of footprints became visible, as if a number of persons had trod back and
forth here.

"What does this mean?" he cried.

Papa Tignol explained shamefacedly: "_We_ did it looking for the pistol; it
was Gibelin's orders."

"_Bon Dieu!_ What a pity! We can never get a clean print in this mess. But
wait! How far along the alleyway did