Vidocq made excellent use of his freedom. He entered freely into all the low haunts of the city, and was received with absolute confidence by every miscreant abroad. Through him, although he kept carefully in the background, innumerable arrests were made; one of the most important was that of the head of a gang of robbers named Guenvive, whose acquaintance he made at a _cabaret_, where they exchanged some curious confidences. Guenvive was very anxious to put him on his guard against "that villain Vidocq," who had turned traitor to his old friends. But Guenvive assured Vidocq that he knew him intimately and there was nothing to be feared while he was by. Together they went to attack Vidocq, each carrying handkerchiefs loaded with two-sous pieces, and watched for him at his front door. For obvious reasons Vidocq did not come out, but his ready concurrence in the scheme made him Guenvive's most intimate friend. The robber was willing to enrol Vidocq in his band, and proposed that he should join in a grand affair in the Rue Cassette. Vidocq agreed, but took no part in the actual robbery on the pretence that he could not safely be out in the streets, as he had no papers. When the party, having successfully accomplished their _coup_, carried their plunder home to Guenvive's quarters, they were surprised by a visit of the police, during which Vidocq, who was present, concealed himself under the bed. The end of this business was the conviction of the robbers and their condemnation to _travaux forcés_, but they appear to have succeeded in discovering how and by whom they had been betrayed. Vidocq brought about another important arrest in the person of Fossard, a notorious criminal, who was to become yet more famous by his celebrated theft of medals from the Bibliothèque Royale. Fossard was a man of athletic proportions and desperately brave; he had escaped from the Bagne of Brest and was supposed to be prepared to go any lengths rather than return there; he was always armed to the teeth, and swore he would blow out the brains of anyone who attempted to take him. He lived somewhere near the Rue Poissonnière; the neighbourhood was known, but not the house or the floor; the windows were said to have yellow silk blinds, but many other windows had the same; another indication was that Fossard's servant was a little humpbacked woman, who also worked as a milliner. Vidocq found the hunchback, but not her master, who had moved into another residence over a wineshop at the corner of the Rue Duphot and the Rue St. Honoré. He at once assumed the disguise of a charcoal-seller, and verified the lodging, but waited for an opportunity to take the criminal. Although he was armed and no coward, he realised that the only safe way to secure Fossard would be in his bed. [Illustration: THE BICÊTRE IN 1710. (_After Gueroult._)]