Old Courtois opened it.
We have already shown the political opinions of the worthy jailer.

He was a royalist.

He therefore felt the deepest sympathy for the four condemned men, and had hoped, like nearly every one in Bourg--like Madame de Montrevel, whose despair at what she had done was known to him--that the First Consul would pardon them.

He had therefore mitigated their captivity as much as possible, without failing in his duty, by relieving them of all needless restrictions.

On the other hand, it is true that he had refused a gift of sixty thousand francs (a sum which in those days was worth nearly treble what it is now) to allow them to escape.
We have seen how, being taken into confidence by his daughter, he had allowed Amelie, disguised as a Bressan peasant, to be present at the trial.