rietor.

"Make a little experiment. Do you mind waiting a couple of minutes? It
_may_ give us a line on this visitor to Number Seven."

"I'll wait," said Gritz.

"Come over here," continued the other. "I'll show you a pistol connected
with this case. And I'll show it to the dog."

"For the scent? You don't think a dog can follow the scent from a pistol,
do you?" asked the proprietor incredulously.

"I don't know. _This_ dog has done wonderful things. He tracked a murderer
once three miles across rough country near Liege and found him hidden in a
barn. But he had better conditions there. We'll see."

They had entered the courtyard now and Coquenil led Caesar to the spot
where the weapon lay still undisturbed.

"_Cherche!_" he ordered, and the dog nosed the pistol with concentrated
effort. Then silently, anxiously, one would say, he darted away, circling
the courtyard back and forth, sniffing the ground as he went, pausing
occasionally or retracing his steps and presently stopping before M. Paul
with a little bark of disappointment.

"Nothing, eh? Quite right. Give me the pistol, Papa Tignol. We'll try
outside. There!" He pointed to the open door where the _concierge_ was
waiting. "Now then, _cherche!_"

In an instant Caesar was out in the Rue Marboeuf, circling again and again
in larger and larger arcs, as he had been taught, back and forth, until he
had covered a certain length of street and sidewalk, every foot of the
space between opposite walls, then moving on for another length and then
for another, looking up at his master now and then for a word of
encouragement.

[Illustration: "'_Cherche!_' he ordered."]

"It's a hard test," muttered Coquenil. "Footprints and weapons have lain
for hours in a drenching rain, but--Ah!" Caesar had stopped with a little
whine and was half crouching at the edge of the sidewalk, head low, eyes
fiercely forward, body quivering with excitement. "He's found something!"

The dog turned with quick, joyous barks.

"He's got the scent. Now _watch_ him," and sharply he gave the word:
"_Va!_"

Straight across the pavement darted Caesar, then along the opposite
sidewalk _away_ from the Champs Elysees, running easily, nose down, past
the Rue Francois Premier, past the Rue Clement-Marot, then out into the
street again and stopping suddenly.

"He's lost it," mourned Papa Tignol.

"Lost it? Of course he's lost it," triumphed the detective. And turning to
M. Gritz: "There's where