Vidocq now took the tavern-keeper into his confidence, warned him that he had under his roof a very dangerous robber, and that this lodger was only waiting a favourable chance to rob his till. The first night that the receipts had been good the ruffian would certainly lay hands upon the money. The tavern-keeper was only too glad to accept the assistance of the police, and promised to admit them whenever required. One night, when Fossard had returned home early and gone to bed, Vidocq and his comrades were let in during the small hours, and the following trick was arranged. The tavern-keeper had with him a little nephew, a child of ten, precocious and ready to earn an honest penny. Vidocq easily taught him a little tale. The child was to go upstairs to Fossard's door in the early morning, and ask Fossard's wife for some eau-de-cologne, saying his aunt was unwell. The child played his part well; he went up, closely followed by the police in stockinged feet; he knocked, gave his message, the door was opened to him, and in rushed the officers, who secured Fossard before he was well awake. In these later days of the First Empire the police, as we have seen, were more actively engaged in political espionage than in the detection of crime, and Paris was very much at the mercy of criminals. There were whole quarters given up to malefactors--places, particularly beyond the Barrier, which offered a safe retreat to convicts, thieves, the whole fraternity of crime, into which no police-officer was bold enough to enter. Vidocq volunteered to clear out at least one of them, a tavern kept by a certain Desnoyez, always a very favourite and crowded resort. Accompanied by a couple of police officers and eight gendarmes, he started off to execute a job for which his superiors declared that he needed a battalion at least. But on reaching the tavern he walked straight into the salon, where a Barrier ball was in progress, stopped the music, and coolly looked around. Loud cries were raised of "Turn him out!" but Vidocq remained imperturbable, and exhibiting his warrant, ordered the place to be cleared. His firm aspect imposed upon even the most threatening, and the whole company filed out one by one past Vidocq, who stationed himself at the door. Whenever he recognised any man as a person wanted or a dangerous criminal, he marked his back adroitly with a piece of white chalk as a sign that he should be made prisoner outside. This was effected by the gendarmes, who handcuffed each in turn, and added him to a long chain of [Illustration: VIDOCQ STOPS THE MUSIC (p. 352).] prisoners, who were eventually conducted in triumph to the Prefecture.