“Naturally,” echoed the fiery little detective.

“I made it my business to place the banker under surveillance, to learn his habits, his ways of life, see who were his friends, the houses he visited.  I soon knew much that I wanted to know, although not all.  But one fact I discovered, and think it right to inform you of it at once.  He was on intimate terms with La Castagneto—­at least, he frequently called upon her.”

“La Castagneto!  Do you mean the Countess of that name, who was a passenger in the sleeper?”

“Beyond doubt! it is she I mean.”  The officials looked at each other eagerly, and M. Beaumont le Hardi quickly turned over the sheets on which the Countess’s evidence was recorded.

She had denied acquaintance with this murdered man, Quadling, and here was positive evidence that they were on intimate terms!

“He was at her house on the very day we all left Rome—­in the evening, towards dusk.  The Countess had an apartment in the Via Margutta, and when he left her he returned to his own place in the Condotti, entered the bank, stayed half an hour, then came out with one hand-bag and rug, called a cab, and was driven straight to the railway station.”

“And you followed?”

“Of course.  When I saw him walk straight to the sleeping-car, and ask the conductor for 7 and 8, I knew that his plans had been laid, and that he was on the point of leaving Rome secretly.  When, presently, La Castagneto also arrived, I concluded that she was in his confidence, and that possibly they were eloping together.”

“Why did you not arrest him?”

“I had no authority, even if I had had the time.  Although I was ordered to watch the Signor Quadling, I had no warrant for his arrest.  But I decided on the spur of the moment what course I should take.  It seemed to be the only one, and that was to embark in the same train and stick close to my man.”

“You informed your superiors, I suppose?”

“Pardon me, monsieur,” said the Italian blandly to the Chief, who asked the question, “but have you any right to inquire into my conduct towards my superiors?  In all that affects the murder I am at your orders, but in this other matter it is between me and them.”

“Ta, ta, ta!  They will tell us if you will not.  And you had better be careful, lest you obstruct justice.  Speak out, sir, and beware.  What did you intend to do?”

“To act according to circumstances.  If my suspicions were confirmed—­”

“What suspicions?”

“Why—­that this banker was carrying off any large sum in cash, notes, securities, as in effect he was.”

“Ah!  You know that?  How?”

“By my own eyes.  I looked into his compartment once and saw him in the act of counting them over, a great quantity, in fact—­”

Again the officials looked at each other significantly.  They had got at last to a motive for the crime.