That evening when Peter strolled into the big reception hall which Mr. Lewinstein had engaged with his private dining-room, his eyes wandered in search of the lady. He knew her by sight--had seen her picture in the illustrated newspapers. He had no difficulty in distinguishing her rather bold features; and, even if he had not, he would have known, from the daring dress she wore, that this was the redoubtable lady whose name had been hinted in connection with one or two unpleasant scandals. But chiefly his eyes were for the great collar of emeralds about her shapely throat. They were big green stones which scintillated in the shaded lights, and were by far the most remarkable jewels in the room. Evidently Lewinstein had explained to Lord Claythorpe the reason of the invitation, because his lordship received him quite graciously and made no demur at a common detective occupying the place by the side of the lady who had so completely enthralled him. It was after the introduction that Peter had a surprise, for he saw Joyce Wilberforce. “I didn’t expect to see you again to-day, Miss Wilberforce,” he said. “I did not expect to come myself,” replied the girl, “but my husband--you knew I was married?” Mr. Dawes nodded. “That is one of the things I did know,” he laughed. “My husband had an engagement, and he suggested that I should amuse myself by coming here. What do you think of the emeralds?” she asked mischievously. “I suppose you’re here to keep a friendly eye on them?” Peter smiled. “They are rather gorgeous, aren’t they? Though I cannot say I admire their wearer.” Peter was discreetly silent. He took the dancer in to dinner, and found her a singularly dull person, except on the question of dress and the weakness of her sister artistes. The dinner was in full swing when Joyce Wilberforce, who was sitting almost opposite the detective, screamed and hunched herself up in the chair. “Look, look!” she cried, pointing to the floor. “A rat!” Peter, leaning over the table, saw a small brown shape run along the wainscot. The woman at his side shrieked and drew her feet up to the rail of her chair. This was the last thing he saw, for at that second all the lights in the room went out. He heard a scream from the dancer. “My necklace, my necklace!” There was a babble of voices, a discordant shouting of instructions and advice. Then Peter struck a match. The only thing he saw in the flickering light was the figure of Lola, with her hands clasped round her neck. The collar of emeralds had disappeared! It was five minutes before somebody fixed the fuse and brought the lights on again. “Let nobody leave the room!” shouted Peter authoritatively. “Everybody here must be searched. And----”