The magistrate, however, was utterly discouraged.  “We must abandon this attempt,” said he.  “All the means of detection have been exhausted.  I give it up.  The prisoner will go to the Assizes, to be acquitted or condemned under the name of May.  I will trouble myself no more about the matter.”

He said this, but the anxiety and disappointment caused by defeat, sneering criticism, and perplexity, as to the best course to be pursued, so affected his health that he became really ill—­so ill that he had to take to his bed.

He had been confined to his room for a week or so, when one morning Lecoq called to inquire after him.

“You see, my good fellow,” quoth M. Segmuller, despondently, “that this mysterious murderer is fatal to us magistrates.  Ah! he is too much for us; he will preserve the secret of his identity.”

“Possibly,” replied Lecoq.  “At all events, there is now but one way left to discover his secret; we must allow him to escape—­and then track him to his lair.”

This expedient, although at first sight a very startling one, was not of Lecoq’s own invention, nor was it by any means novel.  At all times, in cases of necessity, have the police closed their eyes and opened the prison doors for the release of suspected criminals.  And not a few, dazzled by liberty and ignorant of being watched, have foolishly betrayed themselves.  All prisoners are not like the Marquis de Lavalette, protected by royal connivance; and one might enumerate many individuals who have been released, only to be rearrested after confessing their guilt to police spies or auxiliaries who have won their confidence.

Naturally, however, it is but seldom, and only in special cases, and as a last resort, that such a plan is adopted.  Moreover, the authorities only consent to it when they hope to derive some important advantage, such as the capture of a whole band of criminals.  For instance, the police perhaps arrest one of a band.  Now, despite his criminal propensities the captured culprit often has a certain sense of honor—­we all know that there is honor among thieves—­which prompts him to refuse all information concerning his accomplices.  In such a case what is to be done?  Is he to be sent to the Assizes by himself, tried and convicted, while his comrades escape scot free?  No; it is best to set him at liberty.  The prison doors are opened, and he is told that he is free.  But each after step he takes in the streets outside is dogged by skilful detectives; and soon, at the very moment when he is boasting of his good luck and audacity to the comrades he has rejoined, the whole gang find themselves caught in the snare.

M. Segmuller knew all this, and much more, and yet, on hearing Lecoq’s proposition, he made an angry gesture and exclaimed:  “Are you mad?”

“I think not, sir.”

“At all events your scheme is a most foolish one!”