"Jealousy," responded Merrington promptly. "I saw the possibility of that motive as soon as I heard Milly Saker's story, and learnt that Hazel Rath had lived for some years in the moat-house. Young Heredith and she must have been thrown together a lot before the war, and there was doubtless a flirtation between them which probably developed into an intrigue. There are all the materials at hand for it—a well-born idle young man, a girl educated above her station, a lonely country-house, and plenty of opportunity. I know the type of girl well. These half-educated protégées of great ladies grow up with all the whims and caprices of fine females, and their silly little heads are easily turned. Probably this girl imagined that young Heredith was so captivated by her pretty face that he would marry her. When she learnt that she had been dropped for somebody else she brooded in secret until her unbalanced nature led her to commit this terrible crime. Moreover, she is the daughter of a woman with a queer past, who has been living under an assumed name for the past fifteen years."
"Do you think mother and daughter have acted in collusion in this murder?" Caldew asked.
"That is a question I would not care to answer offhand," responded Merrington thoughtfully. "Undoubtedly the mother shielded the daughter and lied to save her, and she obviously knew that the girl was absent from her room at the time the murder was committed. How far this implies guilty knowledge, or the acts of an accomplice, we are not yet in a position to say. We will arrest the daughter, and detain the mother—for the present, at all events. Whether we charge the mother as well as the daughter will depend on our subsequent investigations. It will be no novelty for the mother to be charged as accessory in a murder case," concluded Merrington, with a grim smile.
"We have no direct evidence that the girl went upstairs last night," said Caldew, with a reflective air. "Milly Saker did not see her going upstairs, and apparently nobody saw her coming away."
"No direct evidence, it is true. But the presumptive evidence is so strong that it is hardly needed. In the first place, Milly Saker saw her going down the hall in the direction of the left wing just before the murder was committed. Next day—this morning—the housekeeper sent Milly Saker out of the way before she could be questioned by the police. That act suggests two inferences. First, Mrs. Rath, as she calls herself, had some inkling that Milly Saker saw her daughter in the hall on the previous night, and secondly, that Mrs. Rath feared, in the light of subsequent events, to let it be known that her daughter was seen walking down the hall before the murder was committed. From these inferences we may conclude that, even if the mother had no actual knowledge of the crime, she believed that her daughter was guilty. Her subsequent actions to-day confirm that theory in every respect. And, of course, the recovery of this revolver and the girl's handkerchief in her mother's rooms, where she slept last night, is the strongest possible proof that the girl shot Mrs. Heredith."
"Of course there can be no doubt of that. It would be impossible to find a stronger case of circumstantial evidence," said Caldew earnestly. "But here is a piece of direct evidence. Look here!" He produced the little brooch from his pocket and placed it on the table beside the revolver and the handkerchief. "This is the brooch I told you about. It is the brooch I saw in Mrs. Heredith's room which disappeared while I was downstairs. I found it stuck in a pincushion in the next room, beside the girl's hat. She must have realized that she dropped it in the murdered woman's bedroom, and seized the opportunity to return for it while I was out of the room. That is a piece of direct evidence that she was in Mrs. Heredith's bedroom."
"So you were right about the brooch. I owe you an apology for that, Caldew," said Merrington. He placed the little trinket in his big hand, and turned it over with his finger. The inscription on the back caught his eye, and he held it closer to read it. "Semper Fidelis!" he exclaimed. "The words are typical of the girl. The wishy-washy sentiment would appeal to her, and she's of that partly educated type which thinks a Latin tag imposing. I wonder who gave it to her? Oh, I have it! It was probably a gift from young Heredith, and she added the inscription on her own account so as to enhance the value of the gift and keep her 'Faithful Always.'"
Once more Caldew reluctantly admitted to himself that Merrington's deductions were more swift and vigorous than his own, but he was secretly annoyed to think that the other had gained partly by guesswork the solution of a clue which had caused him so much thought and perplexity.
"The brooch is no more direct evidence than the revolver and handkerchief," continued Merrington. "The girl, unless she is a born fool, is not likely to admit ownership of any one of them. She would be putting the rope round her own neck to do so."
"I realize that," replied Caldew. "But I think that she might be trapped into giving away that she owns the brooch. Women are very impulsive where the loss of ornaments is concerned, and then their actions are instinctive. I have frequently noticed it."