And Raoul, remembering the Persian's remark, thought that it had been mysteriously constructed by the ghost himself.

Later, he learned that Erik had found, all prepared for him, a secret passage, long known to himself alone and contrived at the time of the Paris Commune to allow the jailers to convey their prisoners straight to the dungeons that had been constructed for them in the cellars; for the Federates had occupied the opera-house immediately after the eighteenth of March and had made a starting-place right at the top for their Mongolfier balloons, which carried their incendiary proclamations to the departments, and a state prison right at the bottom.
The Persian went on his knees and put his lantern on the ground.

He seemed to be working at the floor; and suddenly he turned off his light.

Then Raoul heard a faint click and saw a very pale luminous square in the floor of the passage.

It was as though a window had opened on the Opera cellars, which were still lit.