"Then he shall tell his story in your presence," rejoined Mrs. Moxton, quickly, "and you will see that I know nothing." "I shall be glad to be convinced. Tell me, why did you keep silent about this young man?" "Because of the blood marks on the arm of Edgar." "Oh, so you knew the secret of the cryptographic signs, in spite of your denial?" "I did! I do! As a matter of fact, I taught that cryptogram to my--" here Mrs. Moxton closed her mouth with the nervous gesture of one who thinks she is saying too much. "To your sister," finished Ellis, quietly. Mrs. Moxton fenced. "How do you know that I have a sister?" "From the books in your house, some of which contain your name and that of your sister Janet. Also from a cabman on the rank here, who described to me a woman so like you that I am convinced she is your sister--possibly, from the exact likeness, your twin sister." The widow became the colour of chalk at these words. "Where did the cabman see her?" "He drove her to Pimlico on the night, and about the time, your husband was murdered." For a moment or so Mrs. Moxton looked doubtfully at Ellis, and passed her tongue over her dry lips. The doctor could see that she trembled. His unexpected knowledge evidently inflicted a shock on her nerves. Yet, for all her emotion, she still strove to baffle his curiosity. "You seem to know a good deal about my husband," she said irritably. "I do. Because I am anxious to clear your name and extricate you from a difficult position. Mrs. Moxton"--Ellis rose and bent over her with great earnestness--"why will you not be frank with me? You tell me much, but you will not tell me all." She moaned and moved away from him. "Heaven help me, I dare not tell you all." "Yet I am your best friend." "I know it, but you would shrink from me did you know the truth." Ellis took her hand gently. "Tell me who murdered your husband?" he whispered urgently. "I don't know! I swear I don't know!" cried the widow, with much vehemence; "if I did I would tell." "The blood marks hint at Zirknitz." "Yes, yes, but I am sure he is innocent. Rudolph is foolish, vain, shallow, but he never killed Edgar, I swear." "Yet the name on the dead man's arm?" "I don't know the reason of that; I can't say why Edgar wrote it. I read it myself, although I denied all knowledge to you. It was for Rudolph's sake that I lied. I was afraid lest he should get into trouble. I asked him if he was in Dukesfield on that night, but he denies that he was." "And your sister Janet?" A tremor passed through the frame of Mrs. Moxton. "She came to see me on that night, and we quarrelled; she left before Edgar came back, and, I suppose, went crying down the road to take a cab home." "Did she see the murder committed?" asked Ellis, tentatively.