“Don’t trouble,” smiled Tignol.

“It’s no trouble,” declared the stranger.  “On the contrary!” and seizing one of his yellow fangs between thumb and first finger he gave a quick wrench.  “There!” he said with a hideous grin, and he handed Tignol the tooth.

They were just coming into the Auteuil station as this extraordinary maneuver was accomplished.

“I’ll be damned!” exclaimed Tignol.

[Illustration:  “‘There!’ he said with a hideous grin, and he handed Tignol the tooth.”]

“Is it really as good as that?” asked the stranger, in a tone that made the old man jump.

Tignol leaned closer, and then in a burst of admiration he cried:  “Nom de dieu!  It’s Coquenil!”

CHAPTER XX

THE MEMORY OF A DOG

“It’s a composition of rubber,” laughed Coquenil.  “You slip it on over your own tooth.  See?” and he put back the yellow fang.

“Extraordinary!” muttered Tignol.  “Even now I hardly know you.”

“Then I ought to fool the wood carver.”

“Fool him?  You would fool your own mother.  That reminds me—­” He rose as the train stopped.

“Yes, yes?” questioned M. Paul eagerly.  “Tell me about my mother.  Is she well?  Is she worried?  Did you give her all my messages?  Have you a letter for me?”

Tignol smiled.  “There’s a devoted son!  But the old lady wouldn’t like you with those teeth.  Eh, eh!  Shades of Vidocq, what a make-up!  We’d better get out!  I’ll tell you about my visit as we walk along.”

“Where are you going?” asked the detective, as the old man led the way toward the Rue La Fontaine.

“Going to get the dog,” answered Tignol.

“No, no,” objected M. Paul.  “I wouldn’t have Caesar see me like this.  I have a room on the Rue Poussin; I’ll go back there first and take off some of this.”

“As you please,” said Tignol, and he proceeded to give Coquenil the latest news of his mother, all good news, and a long letter from the old lady, full of love and wise counsels and prayers for her boy’s safety.

“There’s a woman for you!” murmured M. Paul, and the tenderness of his voice contrasted oddly with the ugliness of his disguise.

“Suppose I get the dog while you are changing?” suggested Tignol.  “You know he’s been clipped?”

“Poor Caesar!  Yes, get him.  My room is across the street.  Walk back and forth along here until I come down.”

Half an hour later Coquenil reappeared almost his ordinary self, except that he wore neither mustache nor eyeglasses, and, instead of his usual neat dress he had put on the shabby black coat and the battered soft hat that he had worn in leaving the Hotel des Etrangers.

“Ah, Caesar!  Old fellow!” he cried fondly as the dog rushed to meet him with barks of joy.  “It’s good to have a friend like that!  Where is the man who cares so much?  Or the woman either—­except one?”