“The apparition of her own subconscious self,” said the Tracer quietly.  “Science has been forced to admit such things, and, as you know, we are on the verge of understanding the alphabet of some of the unknown forces which we must some day reckon with.”

Harren, tense, a trifle pale, gazed at him earnestly.

“Do you believe in such things?”

“How can I avoid believing?” said the Tracer.  “Every day, in my profession, we have proof of the existence of forces for which we have as yet no explanation—­or, at best, a very crude one.  I have had case after case of premonition; case after case of dual and even multiple personality; case after case where apparitions played a vital part in the plot which was brought to me to investigate.  I’ll tell you this, Captain:  I, personally, never saw an apparition, never was obsessed by premonitions, never received any communications from the outer void.  But I have had to do with those who undoubtedly did.  Therefore I listen with all seriousness and respect to what you tell me.”

“Suppose,” said Harren, growing suddenly red, “that I should tell you I have succeeded in photographing this phantom.”

The Tracer sat silent.  He was astounded, but, he did not betray it.

“You have that photograph, Captain Harren?”

“Yes.”

“Where is it?”

“In my rooms.”

“You wish me to see it?”

Harren hesitated.  “I—­there is—­seems to be—­something almost sacred to me in that photograph. . . .  You understand me, do you not?  Yet, if it will help you in finding her—­”

“Oh,” said the Tracer in guileless astonishment, “you desire to find this young lady.  Why?”

Harren stared.  “Why?  Why do I want to find her?  Man, I—­I can’t live without her!”

“I thought you were not certain whether you really could be in love.”

The hot color in the Captain’s bronzed cheeks mounted to his hair.

“Exactly,” purred the Tracer, looking out of the window.  “Suppose we walk around to your rooms after luncheon.  Shall we?”

Harren picked up his hat and gloves, hesitating, lingering on the threshold.  “You don’t think she is—­a—­dead?” he asked unsteadily.

“No,” said Mr. Keen, “I don’t.”

“Because,” said Harren wistfully, “her apparition is so superbly healthy and—­and glowing with youth and life—­”

“That is probably what sent it half the world over to confront you,” said the Tracer gravely; “youth and life aglow with spiritual health.  I think, Captain, that she has been seeing you, too, during these three years, but probably only in her dreams—­memories of your encounters with her subconscious self floating over continents and oceans in a quest of which her waking intelligence is innocently unaware.”

The Captain colored like a schoolboy, lingering at the door, hat in hand.  Then he straightened up to the full height of his slim but powerful figure.