“I have no definite knowledge, mademoiselle,” I replied, “but can not we, ourselves, investigate the mystery quite as well as the detective Ganimard, the personal enemy of Arsène Lupin?”

“Oh! oh! you are progressing very fast, monsieur.”

“Not at all, mademoiselle. In the first place, let me ask, do you find the problem a complicated one?”

“Very complicated.”

“Have you forgotten the key we hold for the solution to the problem?”

“What key?”

“In the first place, Lupin calls himself Monsieur R⁠⸺.”

“Rather vague information,” she replied.

“Secondly, he is traveling alone.”

“Does that help you?” she asked.