He seemed to see the castle. He seemed to conjure up the mysterious hiding-place. And the vision of an inexhaustible treasure, the dream of chests filled with riches and precious stones could not have excited him more than the idea of those few scraps of paper watched over by the Kaiser's guards. What a wonderful conquest to embark upon! And how worthy of his powers! And what a proof of perspicacity and intuition he had once more given by throwing himself at a venture upon that unknown track! Outside, the men were "working" at the lock. Lupin asked of old Steinweg: "What did the grand-duke die of?" "An attack of pleurisy, which carried him off in a few days. He hardly recovered consciousness before the end; and the horrible thing appears to have been that he was seen to make violent efforts, between his fits of delirium, to collect his thoughts and utter connected words. From time to time, he called his wife, looked at her in a desperate way and vainly moved his lips." "In a word, he spoke?" said Lupin, cutting him short, for the "working" at the lock was beginning to make him anxious. "No, he did not speak. But, in a comparatively lucid moment, he summoned up the energy to make some marks on a piece of paper which his wife gave him." "Well, those marks . . . ?" "They were illegible, for the most part." "For the most part? But the others?" asked Lupin, greedily. "The others?" "There were, first, three perfectly distinct figures: an 8, a 1, and a 3. . . ." "Yes, 813, I know . . . and next?" "And next, there were some letters . . . several letters, of which all that can be made out for certain are a group of three followed, immediately after, by a group of two letters." "'APO ON,' is that it?" "Oh, so you know! . . ." The lock was yielding; almost all the screws had been taken out. Lupin, suddenly alarmed at the thought of being interrupted, asked: "So that this incomplete word 'APO ON' and the number 813 are the formulas which the grand-duke bequeathed to his wife and son to enable them to find the secret papers?" "Yes." "What became of the grand-duke's wife?" "She died soon after her husband, of grief, one might say." "And was the child looked after by the family?" "What family? The grand-duke had no brothers or sisters. Moreover, he was only morganatically and secretly married. No, the child was taken away by Hermann's old man-servant, who brought him up under the name of Pierre Leduc. He was a bad type of boy, self-willed, capricious and troublesome. One day, he went off and was never seen again." "Did he know the secret of his birth?" "Yes; and he was shown the sheet of paper on which Hermann III. had written the letters and figures." "And after that this revelation was made to no one but yourself?" "That's all." "And you confided only in Mr. Kesselbach?"