But then a thing happened that took Beautrelet by surprise. The other man did not cross the river. He watched the old fellow move away and, when he had lost sight of him, turned down a path that took him right across the fields. Beautrelet hesitated for a few seconds as to what course to take, and then quietly decided. He set off in pursuit of the man. “He has made sure,” he thought, “that Gaffer Charel has gone straight ahead. That is all he wanted to know and so he is going—where? To the castle?” He was within touch of the goal. He felt it by a sort of agonizing gladness that uplifted his whole being. The man plunged into a dark wood overhanging the river and then appeared once more in the full light, where the path met the horizon. When Beautrelet, in his turn, emerged from the wood, he was greatly surprised no longer to see the man. He was seeking him with his eyes when, suddenly, he gave a stifled cry and, with a backward spring, made for the line of trees which he had just left. On his right, he had seen a rampart of high walls, flanked, at regular distances, by massive buttresses. It was there! It was there! Those walls held his father captive! He had found the secret place where Lupin confined his victim. He dared not quit the shelter which the thick foliage of the wood afforded him. Slowly, almost on all fours, he bore to the right and in this way reached the top of a hillock that rose to the level of the neighboring trees. The walls were taller still. Nevertheless, he perceived the roof of the castle which they surrounded, an old Louis XIII. roof, surmounted by very slender bell-turrets arranged corbel-wise around a higher steeple which ran to a point. Beautrelet did no more that day. He felt the need to reflect and to prepare his plan of attack without leaving anything to chance. He held Lupin safe; and it was for Beautrelet now to select the hour and the manner of the combat. He walked away. Near the bridge, he met two country-girls carrying pails of milk. He asked: “What is the name of the castle over there, behind the trees?” “That’s the Château de l’Aiguille, sir.” He had put his question without attaching any importance to it. The answer took away his breath: “The Château de l’Aiguille?—Oh!—But in what department are we? The Indre?” “Certainly not. The Indre is on the other side of the river. This side, it’s the Creuse.” Isidore saw it all in a flash. The Château de l’Aiguille! The department of the Creuse! _L’Aiguille Creuse!_ The Hollow Needle! The very key to the document! Certain, decisive, absolute victory! Without another word, he turned his back on the two girls and went his way, tottering like a drunken man. CHAPTER SIX AN HISTORIC SECRET