The word twin sister explained everything that had bewildered him, as in a flash. “I did not know that you had a twin sister,” said Nick. “Yes, I had,” said Mrs. Constant, sadly. “She came to live with me a week ago. She was so happy to come, and this is the end. She died for me.” “Prior to her coming to live with you,” asked Nick, “where did she live?” “In Philadelphia.” “Had she spent much time in New York with you?” “Not much time,” replied Mrs. Constant. “Only for short visits at long intervals.” “Did she have many acquaintances in this city?” Mrs. Constant, as in a flash, saw the end toward which Nick’s questions were tending, and said, hurriedly and impatiently: “Waste no time on that, Mr. Carter. Ethel had no acquaintances in New York, except a very few that she had made within the past week. She was killed because the one who killed her thought it was I who was in the carriage.” “I know that you think so,” said Nick. “But I was trying to explore the possibility of the other view.” “It is wasted time, Mr. Carter. Ethel knew no one in New York, nor had relations with any one who would do such a thing.” “Could any one have followed her from Philadelphia?” “No,” said Mrs. Constant, earnestly. “Ethel was a good girl; she had no secrets apart from me, and no man had entered into her life in any way. She lived a very quiet life at home, and if there had been any love affair of hers or any one persecuting her, I should have known it. My secrets were hers and hers were mine.” “It was not you, then,” asked Nick, “who came to me with that package last night?” “No. I was detained at home by a caller, and as Ethel was going over to a dressmaker’s in Sixth Avenue, I asked her to take that package to you first.” “What time did she leave here to go?” “It must have been nearly eight o’clock. We were going out last evening, but the dress Ethel was to wear had not been sent home as promised, and Ethel wanted to go for it.” “When she gave me that package,” said Nick, “she said she was much hurried. But all the time I thought it was you.” “Yes, the resemblance between us was so great that all our lives we have been mistaken for each other, even by intimate friends. This resemblance is the cause of the announcement in the papers this morning that it was I who had been killed.” “There was no one in the carriage with her when I saw her,” said Nick. “And no one when the carriage arrived home,” replied Mrs. Constant. “But a man did get into that carriage, supposing I was in it, and killed her. I know who it was, and so do you.” Nick raised his hand, warningly, and said: “Mention no names, Mrs. Constant. Charge no one with so awful a deed. Trust to me. I will investigate that line to the end, but let your suspicions be unsaid, or, if you must talk of them, talk only to me.” Mrs. Constant first turned impatiently away, but as impulsively turned back and placed her hand in Nick’s, saying: