The most important fact leading to that inference was that she alone, of all the inmates of the moat-house the previous night, was out of the dining-room when the murder was committed. That supposition took no cognizance of the servants, but Caldew had all along eliminated the servants in his consideration of the crime. In the next place, it supplied an explanation for the disappearance of the bar brooch from the bedroom. In all likelihood the butler had first acquainted his mistress with his discovery of the unlocked staircase door, and she, realizing where she had dropped her brooch, had seized upon the opportunity to request Musard to call the detective downstairs and tell him about the door. In his absence she returned to the bedroom for the brooch. This theory seemed plausible enough at first blush, but as Caldew examined it closely several objections arose in his mind. The hidden motive of the crime, as innocently laid bare by his sister, was strong, but was it strong enough to impel a woman like Miss Heredith, with the rigid principles of her birth, breeding, and caste, and a woman, moreover, who had spent her life in good works, to commit such an atrocious murder? Caldew considered this point long and thoughtfully. With his keener imagination he differed from Merrington by relying to some extent on external impressions, and he could not shake off his first impression of Miss Heredith as a woman of exceptionally good type. He had to admit to himself that her graciousness and dignity were not the qualities usually associated with a murderer. Religion, hypocrisy, smugness, plausibility; these were the commonest counterfeit qualities of criminals; not dignity, worth, and pride. There was, of course, the possibility that Miss Heredith, grown imperious with her long unquestioned sway at the moat-house, had quarrelled with the young wife, and committed the murder in a sudden gust of passion. The most unlikely murders had been committed under the sway of impulse. Caldew recalled that Miss Heredith had been the last person to see the murdered woman alive, and nobody except herself knew what had occurred at that interview. It might be that the young wife had said something to her which rankled so deeply that she conceived the idea of murdering her. Caldew, on reaching this stage of his reasoning, shook his head doubtfully. He had to admit to himself that such a theory did not ring true. If Miss Heredith had been maddened by some insult at the afternoon's interview, she was far more likely to have killed Mrs. Heredith immediately than have waited until dinner-time. And, if she had committed the murder, why had she gone about it in the manner likeliest to lead to discovery, openly leaving her guests a few minutes before, and allowing herself to be seen afterwards descending the staircase? Even the veriest neophyte in crime usually displayed some of the caution of self-preservation.