"That's easily answered. About two years ago I read, in the Journal of Psychology, a paper by your friend, Raoul Arthur, describing the strange mental effect produced on a young man by a dynamite explosion in a South American mine. Arthur is something of an authority in abnormal psychology, and his report of the accident interested me. The name of the young man was not given. I made inquiries long before our chance meeting with you in England. I learned, among other things, who the young man was. Before we met on the Derwentwater, I had watched you at the hotel." "You wrote to Raoul Arthur?" "I did not," he answered drily. "A newspaper account of the accident gave me the clue I needed. According to this account, you were killed in the mine explosion, and no trace of your body or clothing was found. It was long afterwards, in Arthur's report, that your reappearance, under peculiar circumstances, was described. Since then I have learned of your travels. But I have noticed that you always avoid any reference to your South American experiences. So, I appealed to the psychometer." Leighton, absorbed in his notes, was apparently unaware of the eagerness with which David followed his explanation. "It's all very simple," mused the young man. "And yet, it seemed like necromancy." "Science is not necromancy." "But the report," urged David; "I didn't know Raoul had written a report." "You know he is a psychologist, a hypnotist?" "Yes," was the answer, with something of a shudder. "But--why all this elaborate experiment of yours?" "To prove a theory--and to be certain about you." "Why?" "What a question! You expect to marry Una. Before your marriage takes place--if it does take place--I wish to clear up whatever mystery there is hanging over your past." "And your experiment has shown you----?" David asked in a low voice. "It confirms the theories of Tarchanoff and Jung," he replied pedantically. "It proves the intimate connection existing between mental and physical phenomena. The personal result is still incomplete. On that side I must know more." "I will tell you what I can," said David resolutely. "But first--what has Raoul written about me?" "Merely a reference. Read it after you have told me your story. Our experiment is still unfinished, you know." "Unfortunately, I can't tell you the very thing you want to know. The series of words in your test seemed to revive some forgotten nightmare; and the horror of it was that this nightmare kept just beyond my reach--as it always does--its riddle unsolved. This, with your strange knowledge of what had happened, surprised me into this ridiculous weakness." "So I thought," said Leighton. "Now, what do you remember?" "I'll have to go back a little. But--you probably know it all, you know so much of my history." "Never mind. I want you to prove the truth of what I know." David looked at Leighton doubtfully. "Very well," he said, "I'll do what I can."