“Follow that victoria which has just driven off,” he ordered.  “Don’t lose sight of it.  Double fare.”

The trap-door fell, and the man whipped up his horse.

CHAPTER XXXVI

Mr. Sabin received an early visitor whilst still lingering over a slight but elegant breakfast.  Passmore seated himself in an easy-chair and accepted the cigar which his host himself selected for him.

“I am glad to see you,” Mr. Sabin said.  “This affair of Duson’s remains a complete mystery to me.  I am looking to you to help me solve it.”

The little man with the imperturbable face removed his cigar from his mouth and contemplated it steadfastly.

“It is mysterious,” he said.  “There are circumstances in connection with it which even now puzzle me very much, very much indeed.  There are circumstances in connection with it also which I fear may be a shock to you, sir.”

“My life,” Mr. Sabin said, with a faint smile, “has been made up of shocks.  A few more or less may not hurt me.”

“Duson,” the detective said, “was at heart a faithful servant!”

“I believe it,” Mr. Sabin said.

“He was much attached to you!”

“I believe it.”

“It is possible that unwittingly he died for you.”

Mr. Sabin was silent.  It was his way of avoiding a confession of surprise.  And he was surprised.  “You believe then,” he said, after a moment’s pause, “that the poison was intended for me?”

“Certainly I do,” the detective answered.  “Duson was, after all, a valet, a person of little importance.  There is no one to whom his removal could have been of sufficient importance to justify such extreme measures.  With you it is different.”

Mr. Sabin knocked the ash from his cigarette.

“Why not be frank with me, Mr. Passmore?” he said.  “There is no need to shelter yourself under professional reticence.  Your connection with Scotland Yard ended, I believe, some time ago.  You are free to speak or to keep silence.  Do one or the other.  Tell me what you think, and I will tell you what I know.  That surely will be a fair exchange.  You shall have my facts for your surmises.”

Passmore’s thin lips curled into a smile.  “You know that I have left Scotland Yard then, sir?”

“Quite well!  You are employed by them often, I believe, but you are not on the staff, not since the affair of Nerman and the code book.”

If Passmore had been capable of reverence, his eyes looked it at that moment.

“You knew this last night, sir?”

“Certainly!”

“Five years ago, sir,” he said, “I told my chief that in you the detective police of the world had lost one who must have been their king.  More and more you convince me of it.  I cannot believe that you are ignorant of the salient points concerning Duson’s death.”