The Prefect of Police himself directed the attack.  He did so in a straightforward fashion, without beating about the bush, and in a rather harsh voice, which had lost its former tone of sympathy for Don Luis.  His attitude also was more formal and lacked that geniality which had struck Don Luis on the previous day.

“Monsieur,” he said, “circumstances having brought about that, as the residuary legatee and representative of Mr. Cosmo Mornington, you spent the night on this ground floor while a double murder was being committed here, we wish to receive your detailed evidence as to the different incidents that occurred last night.”

“In other words, Monsieur le Prefet,” said Perenna, replying directly to the attack, “in other words, circumstances having brought about that you authorized me to spend the night here, you would like to know if my evidence corresponds at all points with that of Sergeant Mazeroux?”

“Yes.”

“Meaning that the part played by myself strikes you as suspicious?”

M. Desmalions hesitated.  His eyes met Don Luis’s eyes; and he was visibly impressed by the other’s frank glance.  Nevertheless he replied, plainly and bluntly: 

“It is not for you to ask me questions, Monsieur.”

Don Luis bowed.

“I am at your orders, Monsieur le Prefet.”

“Please tell us what you know.”

Don Luis thereupon gave a minute account of events, after which M. Desmalions reflected for a few moments and said: 

“There is one point on which we want to be informed.  When you entered this room at half-past two this morning and sat down beside M. Fauville, was there nothing to tell you that he was dead?”

“Nothing, Monsieur le Prefet.  Otherwise, Sergeant Mazeroux and I would have given the alarm.”

“Was the garden door shut?”

“It must have been, as we had to unlock it at seven o’clock.”

“With what?”

“With the key on the bunch.”

“But how could the murderers, coming from the outside, have opened it?”

“With false keys.”

“Have you a proof which allows you to suppose that it was opened with false keys?”

“No, Monsieur le Prefet.”

“Therefore, until we have proofs to the contrary, we are bound to believe that it was not opened from the outside, and that the criminal was inside the house.”

“But, Monsieur le Prefet, there was no one here but Sergeant Mazeroux and myself!”

There was a silence, a pause whose meaning admitted of no doubt.  M. Desmalions’s next words gave it an even more precise value.

“You did not sleep during the night?”

“Yes, toward the end.”

“You did not sleep before, while you were in the passage?”

“No.”

“And Sergeant Mazeroux?”

Don Luis remained undecided for a moment; but how could he hope that the honest and scrupulous Mazeroux had disobeyed the dictates of his conscience?