The mayor shut his mouth tightly and picked up his hammer.

"Don't be obstinate," I said; "I asked you a question."

"And I refuse to answer," snapped Le Bihan. "Fortin saw what I saw; let him talk about it."

I looked searchingly at the little chemist.

"I don't say that I saw it actually roll up out of the pit, all by itself," said Fortin with a shiver, "but—but then, how did it come up out of the pit, if it didn't roll up all by itself?"

"It didn't come up at all; that was a yellow cobblestone that you mistook for the skull again," I replied. "You were nervous, Max."

"A—a very curious cobblestone, Monsieur Darrel," said Fortin.

"I also was a victim to the same hallucination," I continued, "and I regret to say that I took the trouble to roll two innocent cobblestones into the gravel pit, imagining each time that it was the skull I was rolling."

"It was," observed Le Bihan with a morose shrug.

"It just shows," said I, ignoring the mayor's remark, "how easy it is to fix up a train of coincidences so that the result seems to savor of the supernatural. Now, last night my wife imagined that she saw a priest in a mask peer in at her window——"