They left the hotel by the main entrance, and were just going around into Rue Marboeuf when the concierge from across the way met them with word that Cæsar had arrived.
"Cæsar?" questioned Gritz.
"He's my dog. Ph-h-eet! Ph-h-eet! Ah, here he is!" and out of the shadows the splendid animal came bounding. At his master's call he had made a mighty plunge and broken away from Papa Tignol's hold.
"Good old fellow!" murmured M. Paul, holding the dog's eager head with his two hands. "I have work for you, sir, to-night. Ah, he knows! See his eyes! Look at that tail! We'll show 'em, eh, Cæsar?"
And the dog answered with delighted leaps.
"What are you going to do with him?" asked the proprietor.
"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.