“Good-morning, Emil Sachs,” he said.  “I am glad that you have shown discretion.  Stand there in the light, please, and fold your arms.  Thanks.  Do not think that I am afraid of you, but I like to talk comfortably.”

“I am at monsieur’s service,” the man said in a low tone.

“Exactly.  Now, Emil, before starting to visit you I left a little note behind addressed to the chief of the police here—­no, you need not start—­to be sent to him only if my return were unduly delayed.  You can guess what that note contained.  It is not necessary for us to revert to—­unpleasant subjects.”

The man moistened his dry lips.

“It is not necessary,” he repeated.  “Monsieur is as safe here—­from me—­as at his own hotel.”

“Excellent!” Mr. Sabin said.  “Now listen, Emil.  It has pleased me chiefly, as you know, for the sake of your wife, the good Annette, to be very merciful to you as regards the past.  But I do not propose to allow you to run a poison bureau for the advantage of the Prince of Saxe Leinitzer and his friends—­more especially, perhaps, as I am at present upon his list of superfluous persons.”

The man trembled.

“Monsieur,” he said, “the Prince knows as much as you know, and he has not the mercy that one shows to a dog.”

“You will find,” Mr. Sabin said, “that if you do not obey me, I myself can develop a similar disposition.  Now answer me this!  You have within the last few days supplied several people with that marvelous powder for the preparation of which you are so justly famed.”

“Several—­no, monsieur!  Two only.”

“Their names?”

The man trembled.

“If they should know!”

“They will not, Emil.  I will see to that.”

“The first I supplied to the order of the Prince.”

“Good!  And the second?”

“To a lady whose name I do not know.”

Mr. Sabin raised his eyebrows.

“Is not that,” he remarked, “a little irregular?”

“The lady wrote her request before me in the yellow crayon.  It was sufficient.”

“And you do not know her name, Emil?”

“No, monsieur.  She was dark and tall, and closely veiled.  She was here but a few minutes since.”

“Dark and tall!” Mr. Sabin repeated to himself thoughtfully.  “Emil, you are telling me the truth?”

“I do not dare to tell you anything else, monsieur,” the man answered.

Mr. Sabin did not continue his interrogations for a few moments.  Suddenly he looked up.

“Has that lady left the place yet, Emil?”

“No, monsieur!”

Mr. Sabin smiled.

“Have you a back exit?” he asked.

“None that the lady would know of,” Emil answered.  “She must pass along the passage which borders this apartment, and enter the bar by a door from behind.  If monsieur desires it, it is impossible for her to leave unobserved.”