His brain, moreover, was not as clear as usual. He was obsessed by an idea, the idea of "the other one," the murderer, the assassin, whom he knew to be still clinging to his footsteps. How did that mysterious personality come to be on his tracks? How had he heard of Lupin's leaving prison and of his rush to Luxemburg and Germany? Was it a miraculous intuition? Or was it the outcome of definite information? But, if so, at what price, by means of what promises or threats was he able to obtain it? All these questions haunted Lupin's mind. At about four o'clock, however, after a fresh walk through the ruins, in the course of which he had examined the stones, measured the thickness of the walls, investigated the shape and appearance of things, all to no purpose, he asked the count: "Is there no one left who was in the service of the last grand-duke who lived in the castle?" "All the servants of that time went different ways. Only one of them continued to live in the district." "Well?" "He died two years ago." "Any children?" "He had a son, who married and who was dismissed, with his wife, for disgraceful conduct. They left their youngest child behind, a little girl, Isilda." "Where does she live?" "She lives here, at the end of these buildings. The old grandfather used to act as a guide to visitors, in the days when the castle was still open to the public. Little Isilda has lived in the ruins ever since. She was allowed to remain out of pity. She is a poor innocent, who is hardly able to talk and does not know what she says." "Was she always like that?" "It seems not. Her reason went gradually, when she was about ten years old." "In consequence of a sorrow, of a fright?" "No, for no direct cause, I am told. The father was a drunkard and the mother committed suicide in a fit of madness." Lupin reflected and said: "I should like to see her." The count gave a rather curious smile: "You can see her, by all means." She happened to be in one of the rooms which had been set apart for her. Lupin was surprised to find an attractive little creature, too thin, too pale, but almost pretty, with her fair hair and her delicate face. Her sea-green eyes had the vague, dreamy look of the eyes of blind people. He put a few questions to which Isilda gave no answer and others to which she replied with incoherent sentences, as though she understood neither the meaning of the words addressed to her nor those which she herself uttered. He persisted, taking her very gently by the hand and asking her in an affectionate tone about the time when she still had her reason, about her grandfather, about the memories which might be called up by her life as a child playing freely among the majestic ruins of the castle. She stood silent, with staring eyes; impassive, any emotion which she might have felt was not enough to rouse her slumbering intelligence. Lupin asked for a pencil and paper and wrote down the number 813. The count smiled again.