His overtures thus rejected, and himself still closely pressed by his evil associates, Vidocq passed several anxious months. His fears were verified by the certainty that the suspicions of the police were aroused, and that his house was watched. His arrest seemed imminent, and he was resolved to leave Paris without delay. But he was too late. One morning, in the small hours, a light knock came at the street door. Vidocq felt sure that he was immediately to be arrested. He dressed, and ran quickly up-stairs, got out upon the roof and hid himself behind a stack of chimneys. His surmises were correct, for the house was speedily invested by police agents, who hunted for him high and low, and found him where escape was hopeless except at the risk of breaking his neck. He was carried at once to the Prefecture and into the presence of M. Henri, who remembered him perfectly. The chief, in the interval, had changed his mind. The increase in crime had led him to believe that Vidocq might be usefully employed in laying his hands upon the worst offenders at large. Nothing was said, however, and Vidocq was removed for a third time to Bicêtre, to take his departure with the next chain gang. At Bicêtre, Vidocq wrote privately to the Chief of Police, offering his services afresh. He made no condition but that he should not be sent back to a _bagne_, and expressed his willingness to complete his sentence in any prison in France. M. Henri still hesitated. One argument militated against accepting Vidocq’s proposal. This was the barrenness of the results achieved by others who had promised largely and performed little. Vidocq in his own defence appealed to his good conduct when at large, his continuous efforts to earn an honest livelihood, the production of his books and correspondence and many letters, bearing witness to his probity and good character.
Vidocq was detained between Bicêtre and La Force for nearly two years, and no doubt rendered useful service as _mouton_, the French slang word for a spy who worms himself into the confidence of his fellow prisoners and denounces them. In this way he came upon the addresses of numbers of escaped convicts who were in prison under false names, and was able to give constant information of plots in progress for carrying out new crimes. His reports were closely examined and compared with others, so as to obtain corroboration or the reverse. They were so generally accurate that M. Henri realised the value of this unofficial assistant, and came to the conclusion that such a man would be more useful when free. He was at length released from his probationary detention. To keep up the deception and to screen him from possible suspicion and discovery by the comrades he had betrayed, he was removed from La Force in the ordinary way, handcuffed and under escort, but en route to Bicêtre was permitted to escape. He went at once into hiding, and posed amongst his friends as extraordinarily successful in avoiding recapture. Of course, he carried his life in his hands and would have been instantly sacrificed to the vengeance of those he betrayed, had he been found out. But no one doubted him. He enjoyed unlimited confidence, and was always in high favor with the thieves and bandits, among whom he constantly lived. He was at home in all the lowest dens of Paris, and was a trusted member of the criminal fraternity, all of whom he knew intimately, their favorite haunts and whereabouts and the schemes in which they were engaged. He was frequently invited to join in their depredations and seldom refused, but always carefully avoided taking part in them by failing at the appointed rendezvous or inventing some flimsy excuse for holding aloof. The strange fact is emphasised by Vidocq, that the dangerous classes are singularly simple and unsuspicious. They seemed to take arrest almost as a matter of course, and seldom paused to inquire, when once in custody, how or through whom they had been taken. No one blamed Vidocq, who was their friend, often their hero and model for imitation.