y 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 assistant, 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 wit