A low, startling laugh fell from her lips at the last. She darted across the floor, and flung the door wide, peering out into the darkness. A solemn, awful silence followed, then the door was sharply closed, and the queerly acting girl faced Dyke Darrel once more. She looked weirdly beautiful, with a mass of golden hair falling below her taper waist, her face white as the winter's snow, almost too white for the living. So she stood now; the dancing light from the fire fell full on her countenance, revealing it for the first time plainly to the gaze of the detective. A low, stunned cry escaped from his lips. "My God! It is Sibyl Osborne, the Burlington Captain's daughter." A low laugh fell from the girl's lips. She began humming a gay tune, and danced across the room with arms outstretched, as though attempting to fly. The truth came with stunning force--the poor girl was crazy! Her father, a wealthy Burlington real estate broker, had mysteriously disappeared some months before, and it was supposed that he had met with foul play. Despite the efforts of Dyke Darrel and other detectives, no clew had yet been found of the missing man. The detective had met Sibyl at her father's house, and had regarded her as one both beautiful and accomplished. To meet her as now was a terrible revelation indeed. No wonder Dyke Darrel was stunned. For some moments he stood in pained silence, watching the antics of the poor unfortunate. "Hubert will come, Hubert will come," she sung, as she glided back and forth across the floor. What had caused this awful calamity? Dyke Darrel asked this question in saddened thoughtfulness, as he gazed upon the beautiful wreck before him. "Tell me that Hubert will come, sir, and then I won't believe that he wrote that cruel letter," cried Sibyl, in a mournful voice, pausing in front of the detective. "I cannot tell you unless you show me the letter," returned Dyke Darrel, resolving to humor her. Quickly she drew from her bosom a letter and placed it in the detective's hand. He drew it from the wrapper, hoping to learn something that might give him a clew to the situation. This is what he read: "MISS SIBYL OSBORNE: I am sorry to inform you that I cannot see you again. I am off for Europe on my wedding tour. Forget me as soon as possible. "H. VANDER." "Do you think my Hubert could write anything so cruel?" she questioned, as he handed the missive back to her. "It doesn't seem possible," answered Dyke Darrel. It was evident to his mind that the girl had become crazed on account of her father's disappearance and the treachery of her lover. The detective's heart beat sympathetically for the poor wronged girl. It was his duty to see the girl safely on her way to the Burlington ere he continued his search for the assassins of Arnold Nicholson. One had already given up his account, but there were others yet to punish.