From among that merry throng of strangers, his eyes soon distinguished that one in whom he felt special interest--Mrs. Dupont, dancing now with McDonald, the rather corpulent Major exhibiting almost youthful agility under the inspiration of music. The lady talked with animation, as they circled among the others on the floor, her red lips close to her partner's ear, but Hamlin, suspicious and watchful, noted that her eyes were busy elsewhere, scanning the faces. They swept over him apparently unseeing, but as the two circled swiftly by, the hand resting lightly on the Major's shoulder was uplifted suddenly in a peculiar, suggestive movement. He stared after them until they were lost in the crowd, feeling confident that the motion of those white-gloved fingers was meant as a signal of warning. To whom was it conveyed? He glanced aside at the jam of figures in the doorway. Both the black-whiskered man and Connors had disappeared. It _was_ a signal then, instantly understood and obeyed. The Sergeant had scarcely grasped this fact when his attention was diverted by the appearance of Miss McDonald. She was dancing with a civilian, an immaculately dressed individual with ruddy, boyish face. His intense admiration of his partner was plainly evident, and the girl, simply dressed in white, her cheeks flushed, her dark eyes bright with enjoyment, set Hamlin's cool nerves throbbing. He could not resist gazing at her, and, as their eyes met, she bowed, the full red lips parting in a smile of recognition. There was no reservation, no restraint in that quick greeting, as she whirled by; he could not fail to comprehend its full significance--she had not forgotten, had no desire to forget. What he imagined he read in her face swept all else from his mind instantly, and, with eager eyes, he followed her slight, girlish figure as they circled the hall. The music ceased, and he still watched as the lad led her to a seat, himself sinking into a chair beside her. Then the passing out of several men, who desired return checks, claimed his attention. When the last of these had disappeared, he glanced again in her direction. She was alone, and her young partner was walking toward him across the deserted floor. The lad came to the door, which by now contained few loiterers, and stood there a moment gazing out into the street. "Are you Sergeant Hamlin?" he asked quietly. "Yes." "Miss McDonald requested me to hand you this note unobserved. I have no knowledge of its contents."