The circumstance which put the finishing touch on the moment peculiarly favorable for an attempt at escape, was that the roofers were relaying and re-jointing, at that very moment, a portion of the slates on the prison. The Saint-Bernard courtyard was no longer absolutely isolated from the Charlemagne and the Saint-Louis courts. Up above there were scaffoldings and ladders; in other words, bridges and stairs in the direction of liberty.

The New Building, which was the most cracked and decrepit thing to be seen anywhere in the world, was the weak point in the prison. The walls were eaten by saltpetre to such an extent that the authorities had been obliged to line the vaults of the dormitories with a sheathing of wood, because stones were in the habit of becoming detached and falling on the prisoners in their beds. In spite of this antiquity, the authorities committed the error of confining in the New Building the most troublesome prisoners, of placing there “the hard cases,” as they say in prison parlance.