Lord Hastings called Jack's attention to this. "Oh, I've noticed it," said Jack. "I'll keep an eye on him. Now I wonder what that girl wants with Frank?" Lord Hastings shrugged his shoulders. "You have as much an idea as I have," was his reply. The girl arose from her seat as Frank approached. She extended a hand, and, with the air of a true cavalier, Frank bent low over it. Then, as the music struck up, the girl smiled and would have spoken, but Frank forestalled her. "Will you dance?" he asked. She nodded; and a moment later they were whirling about the floor in an old-fashioned waltz. Thus among the crowd there was a certain privacy and Frank was moved to ask: "And now will you not tell me why you signalled me?" Instantly the girl became serious, although she continued to smile. "I must be brief," she said, "so listen closely. In the first place you are not German. Oh, I knew it the moment you came in," she said hurriedly, as Frank gave a start. "I wouldn't have mentioned it, but the young German officer whom I refused to dance with also suspects. He said as much when he noticed me looking at you. He said he would catch you off your guard and force you to betray yourself." "But----" Frank started to protest. "Oh, there is no use trying to fool me," said the girl. "I know you are not a German--an Englishman perhaps, eh?" Frank smiled at her. "No; not an Englishman," he replied. "You are not French," said the girl, looking up at him. "Even though you speak German without accent, I know you are not French, for I myself am French and I would detect it." "No; I am not French," said Frank with another smile. "Then what?" asked the girl. "Well," said Frank, "what would you say to an American." "An American!" exclaimed the girl. "Are you, really? I am glad, for I have wanted to meet an American." Suddenly Frank gave another start. "Great Scott!" he thought. "Suppose this girl is fooling me? Suppose she has taken this means of finding out who we are?" He looked at her suspiciously. But the girl evidently read his thoughts, for she looked at him steadily and said: "No, I will not betray you. You need have no fear." "But if you are French," said Frank, "what are you doing here?" "It's a long story," said the girl, "and some day I may tell you. But now I have not time. The music will stop in a moment or two now, and you must return to your friends. But I had to warn you, for I know that Lieutenant Holzen is bent on mischief. It would be well for you and your friends to leave at once." "Thanks," said Frank, "but we are able to take care of ourselves." "Oh, I know that," responded the girl. "But I know also that you would not be here except upon some desperate mission and that you cannot afford to jeopardize for the sake of a quarrel." "You are right, of course," said Frank quietly. "But tell me, what is my mission to you?" "Nothing," said the girl slowly, "only that--that I would do anything for France."