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 pass 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 assumes 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!"

Dr. Medjora raised the trap-door, which revealed the secret stairway,
and started down. Mr. Barnes arose to follow him, saying:

"You are taking me to some secret apartment, Doctor. I will go with
you, but this trap must be left open, and I warn you that I am armed."

"You need no weapons, Mr. Barnes. No danger will threaten you. My
purpose in taking you below is entirely different from what you have
in your mind."

At the foot of the stairway he turned aside fr