“Struck it right fust time,” the porter remarked cheerfully.  “This is the man, sir.”

Mr. Sabin turned his head.

“You drove a lady from here to the New York, New Haven & Hartford Depot last Friday?” he asked.

“Well, not exactly, sir,” the man answered.  “The Duchess took my cab, and the first address she gave was the New York, New Haven & Hartford Depot, but before we’d driven a hundred yards she pulled the check-string and ordered me to go to the Waldorf.  She paid me there, and went into the hotel.”

“You have not seen her since?”

“No, sir!”

“You knew her by sight, you say.  Was there anything special about her appearance?”

The man hesitated.

“She’d a pretty thick veil on, sir, but she raised it to pay me, and I should say she’d been crying.  She was much paler, too, than last time I drove her.”

“When was that?” Mr. Sabin asked.

“In the spring, sir,—­with you, begging your pardon.  You were at the Netherlands, and I drove you out several times.”

“You seem,” Mr. Sabin said, “to be a person with some powers of observation.  It would pay you very well indeed if you would ascertain from any of your mates at the Waldorf when and with whom the lady in question left that hotel.”

“I’ll have a try, sir,” the man answered.  “The Duchess was better known here, but some of them may have recognised her.”

“She had no luggage, I presume?” Mr. Sabin asked.

“Her dressing-case and jewel-case only, sir.”

“So you see,” Mr. Sabin continued, “it is probable that she did not remain at the Waldorf for the night.  Base your inquiries on that supposition.”

“Very good, sir.”

“From your manners and speech,” Mr. Sabin said, raising his head, “I should take you to be an Englishman.”

“Quite correct, sir,” the man answered.  “I drove a hansom in London for eight years.”

“You will understand me then,” Mr. Sabin continued, “when I say that I have no great confidence in the police of this country.  I do not wish to be blackmailed or bullied.  I would ask you, therefore, to make your inquiries with discretion.”

“I’ll be careful, sir,” the man answered.

Mr. Sabin handed to each of them a roll of notes.  The cabdriver lingered upon the threshold.  Mr. Sabin looked up.

“Well?”

“Could I speak a word to you—­in private, sir?”

Mr. Sabin motioned Duson to leave the room.  The baggage porter had already departed.

“When I cleaned out my cab at night, sir, I found this.  I didn’t reckon it was of any consequence at first, but from the questions you have been asking it may be useful to you.”

Mr. Sabin took the half-sheet of note-paper in silence.  It was the ordinary stationery of the Waldorf Astoria Hotel, and the following words were written upon it in a faint delicate handwriting, but in yellow pencil:—­