CLYDE BURKE was perplexed. For twenty-four hours, he had been puzzling over the strange revelation made by George Clarendon.

He had thought of it during the evening. It had occupied his mind since his first waking moment in the morning. Now, in his office, Burke still pondered, to no avail.

Clarendon’s discovery that the note signed by Horace Chatham was a forgery was singular enough. But the real cause of Burke’s bewilderment was George Clarendon, himself. The man was an enigma.

Burke realized now how little contact he had had with his benefactor. For months he had forwarded clippings to George Clarendon, yet he had no idea where the man lived.

He sent the clippings when instructed; and the method of transmission was to place the clippings in an envelope and deposit it in the door of a dingy office in a building on Twenty-third Street.

The name on the door was M. Jonas. Burke had never inquired who Jonas might be. He fancied that the man was simply a friend of Clarendon’s. The office had always been locked; and Burke had never seen any one there.

Now Clarendon had appeared; had explained that he was a criminologist; and had partly taken Burke into his confidence.

That was not surprising to Burke. He realized that his mysterious benefactor was a man of intuition.

Clarendon must know that Burke could be trusted.

There is a spirit of loyalty that governs every experienced newspaperman. Clarendon had evidently seen it in Burke.

Sitting at his desk, the ex-reporter reverted to the Wilkinson murder. He examined some of the clippings; then laid them aside, and taking paper and pencil, began to jot down rough ideas.

Granting that Chatham’s note for thirty thousand dollars was a forgery— what did it signify?

The possession of a forged note by Seth Wilkinson might have been a sufficient reason for Chatham to kill the man. Yet that note was dated at the time of the murder!

It could have been made out by no other than Chatham himself— unless Wilkinson had forged it in Chatham’s presence.

Burke had another thought.

Perhaps Chatham had actually signed the note, but had disguised his normal signature. Perhaps Wilkinson had observed the difference, and had mentioned it to Chatham. That might have led to the murder.

But why had Chatham left the false note in Wilkinson’s study?

Burke’s hand was busy as he thought. Almost subconsciously, he was writing the figures 30,000 all over the sheet of paper.

Now he was placing dollar marks in front of the figures on the sheet, and was repeating, half aloud, the words: “Thirty thousand dollars.”

“Quite a bit of money,” said a voice beside him.

Burke nearly toppled from his chair. He looked up, a startled expression on his face, to see George Clarendon standing near him. The man was smiling— that strange smile that Burke had noticed yesterday.

GEORGE CLARENDON sat down in the other chair, and Burke waited for him to speak. The ex-reporter was usually alert; hence he marveled at the way in which Clarendon could arrive, unheard and unseen.

“This case puzzles you,” said the visitor.

Burke nodded.

“I am not surprised,” said Clarendon, “because it has been puzzling to me. Yet I am beginning to form a theory. I take it that you have no theory of your own.”

Burke shook his head.

“You must be right about that forgery, Mr. Clarendon,” he said. “But as far as I can see, it leaves us nowhere. What does it prove?”

“It proves,” said Clarendon quietly, “that something has been learned by rejecting the obvious.

“We have taken the last step in the dramatic murder of Seth Wilkinson— namely, the finding of a promissory note signed by Horace Chatham — and have rejected its accepted significance.

“Now let us go backward, step by step. What happened before that?”

“Chatham was seen leaving Wilkinson’s apartment.”

“By whom?”

“By attendants at the Grampian Apartments. By Wilkinson’s man.”

“Correct. How well did they know Horace Chatham?”

“Well,” said Burke speculatively, “I guess that Wilkinson’s man had seen him a few times; but not very often.” He paused, then added suddenly. “You don’t mean—”

“I mean just what you are thinking,” replied Clarendon, his smile increasing almost imperceptibly. “Just as the police thought they had found a note signed by Chatham, so did those men at the Grampian Apartments think they saw Chatham leave!”

“I see it now!” exclaimed Burke. “It wasn’t Chatham who signed the note. It wasn’t Chatham who killed Wilkinson. But wait! The theory ends right there!

“Wilkinson must have known Chatham well enough not to be mistaken. It must have been Chatham himself who came to see Wilkinson.”

“Do you have Wilkinson’s testimony to that effect?” inquired Clarendon softly.

“Whew!” gasped Burke. “You’re driving it home, now. Perhaps Wilkinson thought it was Chatham, too, until—”

“Until he recognized his error. Then the man disguised as Chatham had only one course — to kill Seth Wilkinson.”

BURKE was groping mentally. Fantastic though the theory might be, it seemed very real to him.

After all, the one man qualified to identify Horace Chatham was dead. Yet he still found it difficult to depart from accepted facts. He was on the point of asking a question when Clarendon forestalled him.

“Let us go back further,” said the man with the masklike face. “You may check me if I am wrong on any detail.

“Horace Chatham was heard to call up Seth Wilkinson. By whom? A man at a cigar counter. He was seen at the Argo Club — but had no sustained conversation with any one. Before that, he was observed at a theater. He was also seen in a ticket agency.

“Is there any witness yet who might not have been easily deceived?”

“No.”

“He also left the Marimba Apartments, after visiting Doctor Albert Palermo. That was just before he went to the theatrical ticket agency. I believe the hallman remembered his departure.

“Am I correct?”

“You are.”

“The hallman, like the others, is a poor witness. But now”— Clarendon was no longer smiling, and his voice was low—”now we have reached a solid link in the chain. Chatham spent some time with Doctor Palermo. We may consider the physician to be a reliable witness.”

Burke nodded his assent.

“Therefore,” concluded Clarendon, “the last man who really and authentically saw Horace Chatham was Doctor Albert Palermo. He is the one who should be questioned as to the identity of Horace Chatham.”

It was amazing to Burke. Yet the newspaperman was used to facts in preference to fancies.

“But so many persons saw Chatham,” he protested weakly. “It seems incredible that everybody could have been deceived—”

“Burke,” interposed Clarendon, with his odd smile, “I know the efficacy of a good disguise. I could cause a dozen people — friends of yours — to swear that they had seen you on Broadway, or in a newspaper office, while you never left this room.

“It is my knowledge of disguise that leads me to suppose — simply to suppose, mind you — that the last person who saw the actual Horace Chatham was Doctor Palermo. That is, if Doctor Palermo saw him.”

“Now it’s becoming more confusing,” objected Burke. “If we reject Doctor Palermo—”

“We are not rejecting him,” returned Clarendon. “It is possible, of course, that Palermo was also duped.

But, there are also other possibilities.

“For example: Palermo may be shielding the false Horace Chatham. Or Chatham may have dropped out of the picture after he left Palermo’s apartment. Or—”

The speaker stopped. He simply spread his hands in an expressive gesture. Somehow, Burke understood the significance more thoroughly than if Clarendon had spoken.

“Perhaps,” murmured the former reporter, “perhaps something happened to Horace Chatham when he was with Doctor Palermo!”

“Exactly.” Clarendon spoke firmly. “That is why, Burke, I expect you to resume an old role tonight — that of a newspaper reporter, seeking an interview. You will call on Doctor Palermo, and question him regarding Horace Chatham.

“Keep all these theories in the back of your head. Use your own judgment; but I would suggest that your theme be the subject of Chatham’s mental condition at the time he called on the eminent psychoanalyst.

“If all is progressing nicely, you may bring up the question of”— the voice almost whispered its final words—”the purple sapphire.”

Clyde Burke was tense for a moment. Then he grinned. It was the greatest assignment he had ever had.

It was like a part in a play— only this was a real drama, with a hidden purpose.

“You can say that you are connected with the Daily Sphere,” came Clarendon’s suggestion. “Many of your friends are there — from the old Clarion staff.”

THE two men descended to the street. As they walked toward Broadway, Clarendon spoke steadily to his companion, in a low, whispered voice that echoed strangely in Burke’s ear.

“Tonight is important,” were the words. “Remember that, Burke! If you uncover important facts, it will be the beginning of a desperate struggle.

“There will be danger — but you are not the man to fear it. Yet danger requires caution.

“Should any strange events develop, you will not see me again— that is, not as George Clarendon.

Instead, you will receive messages— usually written messages.

“These messages will be written in a special ink, Burke. You will reply in kind. A bottle of the ink is on your desk, where I placed it.

“Each word in every message will be written backward. You will write your words backward when you answer.

“Perhaps you are wondering at such a simple code. Yet it serves its purpose; for all messages written with that ink fade completely away a few minutes after they are exposed to the air.”

The men were nearing Broadway. They had reached the fringe of the afternoon crowd. As they turned to cross the street, Clyde Burke was looking straight ahead, toward the surging traffic. Clarendon’s whispering voice was scarcely audible above the din.

“Leave all replies at the Jonas office,” came the final words, “and remember — when you receive a message, read it immediately. For it will fade into nothingness. The words will disappear from your sight, just as I am disappearing—”

It was less than one second before Burke realized that he was no longer listening to the voice of George Clarendon. He turned quickly to look at the man beside him. There was no one there.

Burke glanced up and down the street, peering into the faces of the passers-by. Clarendon was gone.

Yet, while Burke stood alone on the curb, his ears caught the sound of a laugh that he remembered.

Burke looked in vain for the author of the laugh. Then he crossed the street, and mingled, still wondering, with the Broadway throng.

His mysterious companion had vanished like a shadow — yet not even a shadow remained to betray his presence!