"It is fascinating," declared Una emphatically. "Tell us more about it, Uncle Harold. You spoke of an experiment----" "The experiment, by all means," said David. "Just what is it?" "Trapping a ghost," was the laconic answer. "And if you succeed in trapping it----?" "Ah, then--science generally leaves its ghosts to take care of themselves. It's a good rule." "You say you are going to trap a ghost: you don't really mean that," protested Una. "Remember, there are two kinds of ghosts. As a scientist I am not interested in the ghosts of the dead. If they exist outside of fairy tales and theology let some one else hunt them. But I am interested in the other and more profitable kind--the ghosts of the living." "I don't understand," said David. "It needs explanation. Remember what I said as to the phenomena presented by the dreamer, the hypnotic subject, the dipsomaniac, the narcomaniac. In each of these cases one human mind seems capable of division into two independent halves. And each half seems to forget, or to be ignorant of the doings of its mate. Now, I am hunting for this Ghost of the Forgotten." "Sounds romantic," remarked David. "According to your theory, don't you need a hypnotized subject--or at least a dipsomaniac--for your experiment?" "No. The Ghost of the Forgotten lurks in all of us. The man or woman in whom this Ghost is not to be found is exceptional. I doubt if such a being exists--a being whose Book of the Past is as clear, as legible, as his Book of the Present." "But, your experiment, Uncle," demanded Una; "show it to us." "I need help for a satisfactory trial. An experiment isn't a picture, or a book, you know. It needs a victim of some kind. What do you say, David?" he asked, turning abruptly to him. "You want me for the victim?" laughed David. "I'm ready. Feel just like my namesake before he tackled that husky Philistine. Tell me what I'm to do." They were standing at the fireplace, Una with one arm through her lover's, the other resting on her uncle's shoulder. A scarcely perceptible frown clouded Leighton's features before he accepted David's offer. "I merely want you to answer some questions," he said finally. "You will think them trivial; but I want you to answer them under unusual conditions. Let me show you my latest prize and explain things."