"This is an exceedingly grave matter, my dear M. Weber," said Valenglay. "I may add that we can have every confidence in the accuracy of Prince Sernine's statements. I have often met him at dinner. He is a serious, intelligent man. . . ."
"Will you allow me, Monsieur le Président," asked the deputy-chief detective, "to show you another letter which I also received this morning?"
"About the same case?"
"Yes."
"Let me see it."
He took the letter and read:
"Sir,
"This is to inform you that Prince Paul Sernine, who calls himself Mrs. Kesselbach's friend, is really Arsène Lupin.
"One proof will be sufficient: Paul Sernine is the anagram of Arsène Lupin. Not a letter more, not a letter less.
"L. M."