"Mr. Hunter has drawn a strong case against Philip Winthrop, except for one serious flaw," broke in Brett, who had been a silent listener to their argument. "And that is that Philip Winthrop was at the Alibi Club on Monday evening. A number of reputable men are willing to swear to that. It is certain that he could not have been in two places at once. Secondly, Mrs. Winthrop swears that her brother spent Monday evening away from this house." Brett leaned forward and spoke impressively, "Senator Carew was killed by another hand than Philip Winthrop's." "By whose hand?" asked Thornton and Douglas simultaneously. "Captain Frederick Lane." "Fred Lane, of the Engineer Corps?" ejaculated Thornton, much astonished, while Douglas looked as blank as he felt. "Yes, sir." "Bah! you're mad." "Just a moment," Brett held up a protesting hand. "Don't condemn my theory unheard. I seemed up against a blank wall in this house, so to-day I started an investigation at the other end; that is, at the residence of Mr. and Mrs. James Owen, where Miss Cynthia Carew attended a dance on Monday night." "Go on," urged Douglas, as Brett stopped and glanced behind him to see that the hall door was closed. "I called on Mrs. Owen. She was not inclined to be communicative, but her daughter, Miss Alice Owen, who came in during our interview, let the cat out of the bag, and Mrs. Owen had to tell then what she knew, which was this: that Captain Lane and Miss Carew were engaged----" a muttered word escaped Colonel Thornton, and Brett turned to him instantly, "I beg pardon, did you speak?" "No," growled the Colonel. "Apparently they had planned to announce the engagement at the dance," resumed Brett. "Anyway, Miss Owen, who already knew of it, was told by Miss Carew that her uncle, the Senator, refused to give his consent, and had threatened to turn her out of doors if she did not instantly break the engagement." "Poor Cynthia, poor little girl," murmured Thornton, "I am very fond of her, and her father was my most intimate friend. It was beastly of Carew to issue such an ultimatum. She is entirely dependent upon him." "So Miss Owen thought. Miss Carew confided her troubles to her on her arrival. Miss Owen said that while they were sitting in the library Captain Lane came in looking very dejected, and she immediately got up to leave the lovers together. Before leaving the room, however, she overheard Lane tell Miss Carew that he had just seen her uncle, hoping to persuade him to reconsider his refusal, but that he flatly refused to do so in the most insulting terms." "Upon my word, for a mild-tempered man, Carew managed to have plenty of quarrels on his hands on Monday," exclaimed Thornton.