I have among the papers that were sent me by the young man, after the affair was over, a note-book of his, in which a complete account is given of the phenomenon of the disappearance of the “matter” of the assassin, and the thoughts to which it gave rise in the mind of my young friend. It is preferable, I think, to give the reader this account, rather than continue to reproduce my conversation with Rouletabille; for I should be afraid, in a history of this nature, to add a word that was not in accordance with the strictest truth. Chapter XV The Trap (Extract from the Note-Book of Joseph Rouletabille) “Last night—the night between the 29th and 30th of October—” wrote Joseph Rouletabille, “I woke up towards one o’clock in the morning. Was it sleeplessness, or noise without?—The cry of the Bête du Bon Dieu rang out with sinister loudness from the end of the park. I rose and opened the window. Cold wind and rain; opaque darkness; silence. I reclosed my window. Again the sound of the cat’s weird cry in the distance. I partly dressed in haste. The weather was too bad for even a cat to be turned out in it. What did it mean, then—that imitating of the mewing of Mother Angenoux’ cat so near the château? I seized a good-sized stick, the only weapon I had, and, without making any noise, opened my door. “The gallery into which I went was well lit by a lamp with a reflector. I felt a keen current of air and, on turning, found the window open, at the extreme end of the gallery, which I call the ‘off-turning’ gallery, to distinguish it from the ‘right’ gallery, on to which the apartment of Mademoiselle Stangerson opened. These two galleries cross each other at right angles. Who had left that window open? Or, who had come to open it? I went to the window and leaned out. Five feet below me there was a sort of terrace over the semi-circular projection of a room on the ground-floor. One could, if one wanted, jump from the window on to the terrace, and allow oneself to drop from it into the court of the château. Whoever had entered by this road had, evidently, not had a key to the vestibule-door. But why should I be thinking of my previous night’s attempt with the ladder?—Because of the open window—left open, perhaps, by the negligence of a servant? I reclosed it, smiling at the ease with which I built a drama on the mere suggestion of an open window.