On the seat fronting the organ was a book, left behind probably by an oversight. Idris lifted the volume, a handsome one, bound in vellum and gold, and was much surprised at the title.
"Paulus Diaconus de Gestis Langobardorum," he read aloud.
"What a dreadful title!" murmured Beatrice. "What does it mean?"
"It is Paul Warnefrid's History of the Lombards, a book you'll scarcely meet with once in a lifetime. Quite a thrilling work, no doubt, to antiquaries of the Dryasdust order, but I cannot imagine a lady taking to this style of literature. To begin with, it's all in Latin: evidently she understands that language."
"Perhaps the book does not belong to Mademoiselle Rivière."
"The margin of almost every page contains notes in a lady's handwriting—obviously the remarks of one who understands the work. She seems to have been a diligent student," continued Idris, observing the numerous annotations. "Ah! what is this? 'The Fatal Skull,' written across the title-page. On other pages are the initials 'F. S.,' presumably standing for the same words, 'Fatal Skull.' See here, 'F. S.,' and here again, 'F. S.'"
"The Fatal Skull!" said Beatrice in wonderment. "What is meant by that?"
At Beatrice's request Idris translated some of the passages marked with the letters "F. S.," but he failed to grasp their significance, there being no connection whatever between a skull and the subject-matter of the paragraph. Then, becoming conscious that it was an unchivalrous proceeding to pry into an absent lady's book, he was on the point of closing it, when his eye was caught by the following words written upon the fly-leaf:—
Lorelie Rivière,
16, Place Graslin,
Nantes.
"16, Place Graslin?" murmured Idris in great surprise. "Heavens! It was before the door of 16, Place Graslin that M. Duchesne was murdered twenty-seven years ago!"