Seeing that the American really wished to be a friend, and having considerable belief in his cleverness, Arnold related all that had taken place from the time he received the forged letter. When he ended, Tracey expressed a desire to see the letters. But Arnold, unprepared for this conversation, had not brought them with him. "Can you remember the dates?" asked Tracey. "Both were written on the twenty-third." "Hum! And posted on the twenty-fourth. Close running, that." "Only one was posted. That supposed to be an answer from me to Laura." "And the other was brought by a messenger?" asked Tracey. "Yes." "Did you reply to the forged letter?" "No. Remember I only received it late in the afternoon. Believing it really came from Laura, I thought I would see her quicker than a letter could be delivered." "Did Miss Mason look at the post-mark?" "No. She burnt the envelope too." "That's a pity. We might have found in what district the letter was posted. However, we may learn from the district telegraph office, who gave in the letter to be delivered on the twenty-fourth." "We don't know the office." "I'll find it," said Luther coolly, "if I hunt through every office of that sort in London. By the way, when you were in the house did you hear any one about?" "No. Not a soul. And yet----" he hesitated. "Who was singing while you talked to Mulligan?" Arnold jumped up and shuddered. "Tracey, I declare that was the most horrible thing about the business. I don't know." "Yet you were in the room." "I was, and I saw the dead body, which I recognised as that of my cousin. I saw the policeman pass and repass out of the window. Then, thinking he was gone, I went out." "Wait a bit. You told Miss Mason, that you saw him leaning over the gate? Don't make any mistake. This is important." Arnold coloured. "I am telling you the exact truth. I was so confused over the whole business that I mix up things. I left the room before the singing commenced. I waited in the hall for ten minutes, hoping the policeman would not come back. Then I opened the door----" "Hold on a shake. Why didn't you go up and see who was singing?" "Tracey, I couldn't. My nerve was already shaken when I left the room with the dead in it. I recognised my peril, seeing I knew who she was--the dead woman, I mean. In the darkness of the hall I was waiting when I heard a woman's voice singing 'Kathleen Mavourneen.' I was so shaken that I scarcely knew what to do. All my desire was to get away from that horrible house. I opened the door, and saw the policeman at the gate. I hesitated and then faced him--the rest you know." Tracey looked at his pointed boots and considered. "What a fool you were not to steal upstairs and see who was singing. You might have found the murderess." "Murderess!" "Yes," said Tracey, getting off the couch, "from the fact of the singing I guess it was a woman who killed Mrs. Brand."