The elegant grounds, covering nearly an entire square, were almost as bright as day under the glare of a myriad of electric lights suspended among the trees of the surrounding park. The superb mansion itself was ablaze from basement to roof. Its broad halls and spacious, sumptuously furnished rooms were thronged with masked guests, many in elaborate fancy and historic costumes, and some in nondescript attire. Courtiers and princes rubbed elbows with clowns and jesters. Queens in regal raiment hobnobbed in corners and alcoves with country bumpkins, while the whirl of the dance presented a kaleidoscopic picture, the details of which would require a volume. It was a weird, yet dazzling picture, with the gleam and glitter of jewels of inestimable worth. Aside from the numerous officers and guardians in and about the extensive grounds, guardians of diamonds and gems that would have aggregated millions, two men in evening dress and of refined and unofficial bearing mingled with the servants and other house functionaries in various parts of the mansion, apparently having only an eye to the general conduct of affairs. These two men were Nick Carter and his chief assistant, Chick Carter, both carefully disguised, the balmasque feature of the gathering and the unusual opportunity for knavery that it presented, in view of costly jewels worn by his guests, having led their host to secretly employ the two famous detectives as safeguards against designing intruders and possible crime. At precisely half past ten, the fateful moment mentioned, Nick Carter was standing in the main hall and near the front door of the house. He could see the entire length of the hall, the broad stairway to the second floor, and through several open doors the throng of dancers in the adjoining rooms. All of them still wore masks, eleven o’clock having been the hour stipulated for their removal. Mingled with the strains of orchestral music the single stroke of the clock reached the detective’s ear. There was no mistaking the sweet and mellow resonance of its bell. At the same moment a woman, threading her way between numerous other persons in the hall caught the detective’s eye. She was one of the guests, and her costume spoke for itself. She was clad completely in black, from her dainty ties to the mask that hid her face and the veil that partly concealed her hair and fell in picturesque folds over her shapely neck and shoulders. But this ebon costume was bespangled with countless glittering stars and radiant diamonds. Plainly enough, she was a personification of--Night. Nick thought it a striking costume, one that set off to advantage the fine, graceful form of the woman. He watched her furtively while she came through the hall and went up the stairs to the second floor. He could see the gleam and glitter of her eyes, but no other feature of her face, yet he felt sure she was comparatively young and beautiful.