Mr. Barnes was sitting in his office, looking listlessly over his morning paper, when his eye suddenly met a headline announcing the death of Madame Medjora. Instantly his interest was aroused, and he read the account with avidity until he reached the statement that the disease of which Madame had died was diphtheria. Then he put his paper down upon his desk, slapped his hand upon it by way of emphasis, and e.j.a.c.u.l.a.t.ed:

"Foul play, or my name is not Barnes!"

He remained still for a few moments, thinking deeply. Then he resumed his reading. When he had reached the end, he started up, gave a few hurried instructions to his a.s.sistant, and went out. He visited the Academy of Medicine and obtained permission to enter the library, where he occupied himself for a full hour, making a few memoranda from various books. Next he proceeded in the direction of Villa Medjora, and arriving there he asked to see Leon Grath.

Leon entered the reception-room in some surprise, and seeing Mr.

Barnes he asked:

"Is your errand of importance? We have death in the house."

"It is in connection with the death of Madame Medjora that I have called to see you, Mr. Grath. I am a detective!"

The effect of this announcement was electrical. Leon turned deathly pale, and dropped into a seat, staring speechless at his visitor. Mr.

Barnes also chose to remain silent, until at last Leon stammered forth:

"Why do you wish to see me?"

"Because I believe that you can throw some light upon this mysterious subject."

"Mysterious subject? Where is the mystery? The cause of Madame's death is clearly known!"

"You mean that she died of diphtheria. Yes, that is a fact. But how did she contract that disease? Is that clearly known? Can you throw any light upon that phase of the question?"

Leon controlled his agitation with great difficulty. He had thought, when urged on by that terrible temptation which he had resisted, that a death such as this would arouse no suspicion. Yet here, while the corpse was yet in the house, a detective was asking most horribly suggestive questions. Questions which had haunted him by day and by night, ever since that visit to the laboratory.

"I am not a physician," at length he murmured. "I am merely a student."

"Exactly! You are a student in the laboratory of Dr. Medjora. You can supply the information which I seek. Do you know whether, three days ago, there was a culture of the bacillus of diphtheria in the Doctor's laboratory?"

"Why do you ask? What do you suspect?"

Leon was utterly unnerved, and stammered in his utterance. He made a tremendous effort, in his endeavor to prevent his teeth from chattering, and barely succeeded. Indeed, his manner was so perturbed that for an instant Mr. Barnes suspected that he was guilty of some connection with Madame's death. A second later he guessed the truth, that Leon's suspicion's were identical with his own.

"What I think," said Mr. Barnes, "is not to the point. My question is a simple one. Will you reply to it?"

"Well, yes! We did have such a culture tube in the laboratory."

"Did have," said the shrewd detective, quickly. "Then it is not there now. Where is it?"

"I do not know. I think the Doctor took it away. Of course he used it in some harmless experiment, or--or--or--or for making slides for the microscope."

"You mean that you surmise this. All you know is that Doctor Medjora took the tube out of the laboratory. Am I not right? Now when did that occur? You saw him take it, did you not?"

Leon stared helplessly at his tormentor for a moment, great beads of perspiration standing on his brow. Then starting to his feet he exclaimed:

"I will not answer your questions! I have said too much! You shall not make me talk any more," and with a mad rush he darted from the room, and disappeared upstairs.

Mr. Barnes made no effort to arrest his flight. Indeed he sympathized with the lad, well comprehending the mental torture from which he suffered. He pondered over the situation awhile, and finally appeared to have decided upon a plan of action. He took a card from his case, and wrote upon it these words:

"Mr. Barnes, detective, would like to see Dr. Medjora, concerning the coincidence of the death of his two wives.

This matter is pressing, and delay useless."

This he placed in an envelope which he took from a desk that stood open, and then he touched a gong, which summoned a servant.

"Hand this to Dr. Medjora, immediately. I will await a reply here."

Ten minutes elapsed, and then the servant returned, and bidding Mr.

Barnes follow him, led the way to the laboratory. Here Dr. Medjora received the detective, as though he were a most welcome visitor.

"So, Mr. Barnes," said the Doctor, opening the conversation, "you have attained your ambition, and are now a full-fledged detective. I have read something of your achievements, and have watched your progress with some interest. I congratulate you upon your success."

"Dr. Medjora," said the detective, with much dignity, "the object of my visit is so serious that I cannot accept flattery. We will proceed to business, if you please."

"As you choose! Let me see! From your card, I judge that you fancy that there is some suspicious circ.u.mstance about my late wife's death.

You speak of a coincidence which connects hers with that of my first wife. What is it?"

"Both died of diphtheria," said Mr. Barnes, impressively.

"You are entirely mistaken, sir," said the Doctor, with a touch of anger. "My first wife, Mabel, died of morphine, self-administered, and fatal because of other organic disease from which she suffered. She did not die of diphtheria."

"A physician so testified, and signed a death certificate to that effect."

"He did, but he was mistaken. Physicians are mortal as other men are, and as liable to errors of judgment. I repeat, Mabel died of poison."

"Well, we will pa.s.s that for a moment. Your last wife died of diphtheria, and she did not contract that disease legitimately."

"No? You interest me. Pray then how did she contract it?"

"By inoculation with the bacillus of diphtheria, Dr. Medjora, and you administered this new form of poison, which an autopsy does not disclose."

"Quite an ingenious theory, Mr. Barnes, and I admire your skill in evolving it. It shows what an enterprising detective you are. You think that if you make a discovery of this nature, you will cover yourself with glory. Only you are wrong. I did not do what you charge.

Why should I wish to kill my wife?"

"Because she had discovered your secret!"

"What secret?"

"That Leon is the child of Mabel Sloane and yourself!"

"Mabel Medjora, you mean," said the Doctor, sternly. "When a woman marries, she a.s.sumes her husband's name."

The Doctor was apparently very jealous of the good name of his first wife. Mr. Barnes was amazed at this exhibition of feeling. The Doctor continued, as though soliloquizing:

"So you are the detective that my wife engaged? Strange fatality! Very strange!" He walked up and down the room a few times, and then confronted the detective.

"Mr. Barnes," said he, "it is evident that you and I must have a serious and uninterrupted conversation. Leon may come in here at any moment. Will you accompany me to a room below, where we will be safe from intrusion?"

"Certainly!"