“All right, Burger!  I think it is very kind of you to let me into this secret, and I promise you that I will write nothing about it until you have published your report.  Good-bye for the present!  You will find me at the Gate at twelve.”

The cold, clear air was filled with the musical chimes from that city of clocks as Burger, wrapped in an Italian overcoat, with a lantern hanging from his hand, walked up to the rendezvous.  Kennedy stepped out of the shadow to meet him.

“You are ardent in work as well as in love!” said the German, laughing.

“Yes; I have been waiting here for nearly half an hour.”

“I hope you left no clue as to where we were going.”

“Not such a fool!  By Jove, I am chilled to the bone!  Come on, Burger, let us warm ourselves by a spurt of hard walking.”

Their footsteps sounded loud and crisp upon the rough stone paving of the disappointing road which is all that is left of the most famous highway of the world.  A peasant or two going home from the wine-shop, and a few carts of country produce coming up to Rome, were the only things which they met.  They swung along, with the huge tombs looming up through the darkness upon each side of them, until they had come as far as the Catacombs of St. Calixtus, and saw against a rising moon the great circular bastion of Cecilia Metella in front of them.  Then Burger stopped with his hand to his side.  “Your legs are longer than mine, and you are more accustomed to walking,” said he, laughing.  “I think that the place where we turn off is somewhere here.  Yes, this is it, round the corner of the trattoria.  Now, it is a very narrow path, so perhaps I had better go in front, and you can follow.”  He had lit his lantern, and by its light they were enabled to follow a narrow and devious track which wound across the marshes of the Campagna.  The great Aqueduct of old Rome lay like a monstrous caterpillar across the moonlit landscape, and their road led them under one of its huge arches, and past the circle of crumbling bricks which marks the old arena.  At last Burger stopped at a solitary wooden cowhouse, and he drew a key from his pocket.

“Surely your catacomb is not inside a house!” cried Kennedy.

“The entrance to it is.  That is just the safeguard which we have against anyone else discovering it.”

“Does the proprietor know of it?”

“Not he.  He had found one or two objects which made me almost certain that his house was built on the entrance to such a place.  So I rented it from him, and did my excavations for myself.  Come in, and shut the door behind you.”

It was a long, empty building, with the mangers of the cows along one wall.  Burger put his lantern down on the ground, and shaded its light in all directions save one by draping his overcoat round it.  “It might excite remark if anyone saw a light in this lonely place,” said he.  “Just help me to move this boarding.”  The flooring was loose in the corner, and plank by plank the two savants raised it and leaned it against the wall.  Below there was a square aperture and a stair of old stone steps which led away down into the bowels of the earth.