The men examined the cement which held the heavy stone in its place.
"It will take time," one of them said. "This cement is terribly hard; we shall have to chip every bit of it away."
"You must do your best," said the Man in Grey earnestly. "A human life may depend on your toil. You will have no cause to grumble at the reward when your work is done. For reasons which I cannot explain, I may not bring any strangers to help you. So work away as hard as you can. I will return in about an hour with Monsieur le Sous-Préfet."
He waited to see the men swing their picks, then turned on his heel and started to walk back the way he came.
It was nearly two hours before the slab of granite was finally removed from its place. M. le Sous-Préfet was standing by with the Man in Grey when the stone was hoisted up and turned over. It disclosed a large cavity with, at one end of it, a flight of stone steps leading downwards.
"Now then, Monsieur le Sous-Préfet," said the police agent quietly, "will you follow me?"
M. Leblanc's face was ghastly in its pallor. The sudden hope held out to him by the Man in Grey had completely unnerved him. "Are you sure——" he murmured.
"That we shall find Monsieur Ernest down there?" broke in the other, as he pointed to the hollow. "Well, Monsieur le Sous-Préfet, I wish I were equally sure of a fortune!"
He had a lighted lantern in his hand and began to descend the stone stairs, closely followed by the sous-préfet. The labourers above were resting after their heavy toil. They could not understand all they had seen, and their slow wits would probably never grasp the full significance of their strange adventure. While in the depths below the Man in Grey, holding M. le Sous-Préfet by the arm and swinging the lantern in front, was exploring the mediæval lurking-holes of the Huguenots, the three labourers were calmly munching their bread and cheese.