Imprisoned at Bicêtre, Vidocq is reunited with his comrade Henri Desfossés. Wounded in the leg so as not to leave with the chain, Vidocq reveals to Desfossés that there is a tunnel dug into the courtyard of the madhouse. But not only are the madmen more dangerous than the guards, the coachman hired by Annette wants to be paid immediately, and Vidocq must return to prison to retrieve the money confiscated from him...