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.