“I know it, we call it the glycine room. But how will you find it? There are three staircases and a labyrinth of passages. I can give you the clue and explain the way to you, but you would get lost just the same.”

“Come with me,” said Beautrelet, laughing.

“I can’t. I have promised to go to my mother in the South.”

Beautrelet returned to the friend with whom he was staying and began to make his preparations. But, late in the day, as he was getting ready to go, he received a visit from Valméras.

“Do you still want me?”

“Rather!”

“Well, I’m coming with you. Yes, the expedition fascinates me. I think it will be very amusing and I like being mixed up in this sort of thing.—Besides, my help will be of use to you. Look, here’s something to start with.”

He held up a big key, all covered with rust and looking very old.

“What does the key open?” asked Beautrelet.

“A little postern hidden between two buttresses and left unused since centuries ago. I did not even think of pointing it out to my tenant. It opens straight on the country, just at the verge of the wood.”