“Oh,” replied Mrs. Carew, “the whistle, you mean. That is our family signal. The children were in the habit of calling each other by that means in bygone years. I expect they are in the garden now, and wish us to join them.” Mrs. Carew knew that Molly was not in the garden, but in making this intentional mistake she showed the wisdom of her kind. “It seems to me,” said Signor Bruno, “that the air--the refrain, one might call it--is familiar.” Christian Vellacott smiled suddenly behind his screen of flowers, but did not move or look up. “I expect,” explained Sidney, “that you have heard the air played upon the bugle. It is the French 'retraite,' played by the patrol in garrison towns at night.” In the meantime Christian had cut the fly-leaf from the book before him, and, after carefully folding it, he placed the paper in his breast-pocket. Then he rose and passed out of the open window into the garden. Immediately Signor Bruno asked his hostess a few polite questions regarding her guest--what was his occupation, how long he was going to stay, and whether she did not agree with him in considering that their young friend had a remarkably interesting face. In the course of his remarks the old gentleman rose and crossed to the table where Christian had been sitting. There was a flower there which he had not seen in England before. Absently he took up the book which Christian had just been studying, and very naturally turned to the title-page. The fly-leaf was gone! When he laid the volume down again he replaced it in the identical position in which he had found it. CHAPTER IX A CLUE When Christian left the drawing-room he walked quickly down the moss-grown path to the moat. Hilda was standing at the edge of the dark water, and as he joined her she turned and walked slowly by his side. “You are a most unsatisfactory person,” she said gravely after a few moments. He looked down at her without replying. His eyes softened for a moment into a smile, but his lips remained grave. “You deliberately set yourself,” she continued, “to shatter one illusion after another. You have made me feel quite old and worldly to-night, and the worst of it is that you are invariably right. It is most annoying.” Her voice was only half-playful. There was a shade of sadness in it. Christian must have divined her thoughts, for he said: “Do not let us quarrel over Signor Bruno. I dare say I am wrong altogether.” She looked slowly round. Her eyes rested on the dark surface of the water, where the shadows lay deep and still; then she raised them to the trees, clearly outlined against the sky. “I suppose that such practical, matter-of-fact people as you are proof against mere outward influences.”