They found themselves soon in a little box, small even for two people. Henriette settled down, almost from the first, to enjoy the performance. She laughed at the whimsical Frenchman, applauded the versatile leading lady, entered with wonderful facility into the spirit of the place. And then, some half-hour after their entrance, Aaron Rodd felt the fingers which he was holding under cover of a programme suddenly twitch. He glanced up. To his amazement, all the joy and light-heartedness had passed from her face. Her features seemed as though they might have been carved out of a piece of ivory. Her lips were a little parted, her eyes filled with fear. She was gazing with strange intensity upon the figure of a girl who, heralded by much applause, had suddenly bounded on to the stage. He leaned towards her. "Is anything wrong, Henriette?" he asked softly. She roused herself a little. "Yes!" she whispered. "That girl--do you see what she is wearing--around her neck?" He glanced down on to the stage in puzzled fashion. The girl in question, French and a new-comer, who was singing a little song of the boulevards with a good deal of appropriate action, wore no jewellery except a single rather curious yellow stone, suspended from her neck by a platinum chain. "You mean that yellow thing?" She looked at him in surprise. "But of course you do not know!" she exclaimed. "That is the great yellow diamond. It belongs to----" "To whom?" he interrupted eagerly. "To Leopold's--to my brother's collection," she explained hesitatingly. He was puzzled for a moment. Then the sense of her words, and their import, began to dawn upon him. "You mean that the stone is amongst those that your brother has acquired?" he continued diffidently--"one of those he has not yet tried to have recut?" "Yes!" she murmured. There was a moment's embarrassed silence. Henriette was obviously distraught. She watched the rather fascinating figure upon the stage with strained eyes. "It isn't," she went on, turning abruptly to her companion, "that I mind if Leopold chooses to amuse himself. He has probably lent the girl the diamond for her first appearance. I see that it is her debut to-night. It is not that. But he is so rash, so daring. That stone is known throughout the world--its history, its description have been published everywhere. Why, if there is anyone in the house who knows anything of the history of gems, they will recognise it. It will be traced--so easily traced to Leopold. Oh, what folly! I must go and see her. I must go at once!" She rose to her feet. They drew a little into the background of the box. "I am afraid it will be rather difficult," Aaron Rodd warned her. "It must be arranged," she insisted. "We will go together and find some one at the box office who will take a message round."