“And that will assist us very much,” growled Gevrol.  The sergeant-major, to his great relief, now received permission to retire, but not without having been warned that very probably the commissary would require his deposition.  The moment had come to search the garments of the pretended soldier, and the commissary, who performed this duty himself, hoped that some clue as to the man’s identity would be forthcoming.  He proceeded with his task, at the same time dictating to one of the men a proces-verbal of the search; that is to say, a minute description of all the articles he found upon the dead man’s person.  In the right hand trousers pocket some tobacco, a pipe, and a few matches were found; in the left hand one, a linen handkerchief of good quality, but unmarked, and a soiled leather pocket-book, containing seven francs and sixty centimes.

There appeared to be nothing more, and the commissary was expressing his regret, when, on carefully examining the pocket-book he found a compartment which had at first escaped his notice, being hidden by a leather flap.  This compartment contained a carefully folded paper.  The commissary unfolded it and read the contents aloud: 

“My dear Gustave,—­To-morrow, Sunday evening, do not fail to come to the ball at the Rainbow, according to our agreement.  If you have no money pass by my house, and I will leave some with the concierge, who will give it to you.

“Be at the ball by eight o’clock.  If I am not already there, it will not be long before I make my appearance.  Everything is going on satisfactorily.

“Lacheneur.”

Alas! what did this letter reveal?  Only that the dead man’s name was Gustave; that he had some connection with a man named Lacheneur, who had advanced him money for a certain object; and that they had met at the Rainbow some hours before the murder.

It was little—­very little—­but still it was something.  It was a clue; and in this absolute darkness even the faintest gleam of light was eagerly welcomed.

“Lacheneur!” growled Gevrol; “the poor devil uttered that name in his last agony.”

“Precisely,” insisted Father Absinthe, “and he declared that he wished to revenge himself upon him.  He accused him of having drawn him into a trap.  Unfortunately, death cut his story short.”

Lecoq was silent.  The commissary of police had handed him the letter, and he was studying it with the closest attention.  The paper on which it was written was of the ordinary kind; the ink was blue.  In one of the corners was a half-effaced stamp, of which one could just distinguish the word—­Beaumarchais.

This was enough for Lecoq.  “This letter,” he thought, “was certainly written in a cafe on the Boulevard Beaumarchais.  In which one?  I must ascertain that point, for this Lacheneur must be found.”