"It's a strange tale, Senor," he commented when Herran had come to the end. "These things with a touch of mystery in them are always fascinating--until you stumble on the clew. Then it's very simple. I suppose you have no theory to explain our friend's disappearance?" "None, Senor." "You have just told me, Mr. Leighton," he went on, addressing the latter, "that you are here to add to your knowledge of psychology." "I did." "Well, what do you make of it? Here's what you are looking for--a neat psychological problem right to your hand." "I don't see it," said the savant impatiently. "That's always the way with you great scientists! But--it's simple," declared Raoul, a note of triumph in his voice; "absolutely simple--if you know David as well as I do." "I said that you probably know him better. I have not known him as long or as intimately as you have. But--again I fail to see what psychology has to do with it." "It has everything to do with it. David was not spirited away, as you seem to imagine. He disappeared of his own accord." "There is every reason to think the contrary," said Leighton contemptuously. "Oh, of course I may be wrong in my theory. But, as there is no other evidence, I see only one solution. It's the clew we are after, you know--and the clew is right under your nose." "Perhaps you are on the wrong scent. Some investigators have a knack of being cocksure about everything. But--explain your meaning." "Very well. Let's talk as one psychologist to another, then. Meudon has a peculiar temperament. You probably know that. But you may not know that the dual personality is highly developed in him. Under strong, sudden excitement this personality becomes greatly exaggerated." "He was laboring under no particular excitement at the time of his disappearance," objected Leighton. "What about the mission he was on? I have an idea that it was of absorbing importance to him. Remember, he was revisiting scenes connected with an episode that for some years he has been trying to forget but which he now wants to revive. And then, to cap the climax, suddenly he comes, slap bang, right into the midst of a rabble of peons who would be only too glad to kill him, or imprison him, or torture him--or anything else unpleasant. The same crowd tried to get me once, so I know what it all means." "All this is true; but the excitement was hardly enough to drown David's normal personality." "It all helps, though. It predisposes things. It is, as I look at it, the final stage setting, with all the characters in their places awaiting the entrance of the villain to finish up the tragedy. And in this case the villain entered just at the critical moment. Mr. Leighton," he asked abruptly, "have you ever known David to drink a glass of wine?" "I can't say that I have," he answered doubtfully. "Well, alcoholic stimulus, with certain temperaments--you know what it does. It starts up an altogether abnormal psychology, doesn't it?" "Very apt to."