At about eleven o'clock in the evening of the 20th of February, 186--, which chanced to be Shrove Sunday, a party of detectives left the police station near the old Barriere d'Italie to the direct south of Paris. Their mission was to explore the district extending on the one hand between the highroad to Fontainebleau and the Seine, and on the other between the outer boulevards and the fortifications. This quarter of the city had at that time anything but an enviable reputation. To venture there at night was considered so dangerous that the soldiers from the outlying forts who came in to Paris with permission to go to the theatre, were ordered to halt at the barriere, and not to pass through the perilous district excepting in parties of three or four. After midnight, these gloomy, narrow streets became the haunt of numerous homeless vagabonds, and escaped criminals and malefactors, moreover, made the quarter their rendezvous. If the day had been a lucky one, they made merry over their spoils, and when sleep overtook them, hid in doorways or among the rubbish in deserted houses. Every effort had been made to dislodge these dangerous guests, but the most energetic measures had failed to prove successful. Watched, hunted, and in imminent danger of arrest though they were, they always returned with idiotic obstinacy, obeying, as one might suppose, some mysterious law of attraction. Hence, the district was for the police an immense trap, constantly baited, and to which the game came of their own accord to be caught. The result of a tour of inspection of this locality was so certain, that the officer in charge of the police post called to the squad as they departed: "I will prepare lodgings for our guests. Good luck to you and much pleasure!" This last wish was pure irony, for the weather was the most disagreeable that could be imagined. A very heavy snow storm had prevailed for several days. It was now beginning to thaw, and on all the frequented thoroughfares the slush was ankle-deep. It was still cold, however; a damp chill filled the air, and penetrated to the very marrow of one's bones. Besides, there was a dense fog, so dense that one could not see one's hands before one's face.