“Yes, sir.  Will you hold the iron while I get a light?  He might try to jump out, and he may have firearms.  Thank you, sir.”

Masin produced a short black pipe, filled it and lighted it.

“I was thinking, sir,” he said, as he threw away the wooden match, “that if we kill him here we may have trouble in disposing of his body.  Thank you, sir,” he added as he took over the drill again and made it clang on the stones.

“There will be no trouble about that,” Malipieri answered, speaking over the hole.  “We can drop him down the overflow shaft in the passage.”

“Where do you think the shaft leads, sir?” asked Masin, grinning with delight.

“To some old drain and then to the Tiber, of course.  The body will be found in a week or two, jammed against the pier of some bridge, probably at the island of Saint Bartholomew.”

“Yes, sir.  But the drain is dry now.  The body will lie at the bottom of the shaft, where we drop it, and in a few days the cellars will be perfumed.”

He laughed roughly at his horrible joke, which was certainly calculated to affect the nerves of the intruder who was meant to hear it.  Malipieri began to wonder when the man would give a sign of life.

“We can fill the well by plugging the arch in the outer chamber,” he suggested.  “Then the water will pour down the shaft and wash the body away.”

“Yes, sir,” assented Masin.  “That is a good idea.  Shall I go down and kill him now, sir?”

“Not yet,” Malipieri answered, knocking the ash from his cigar.  “We have not finished smoking, and there is no hurry.  Besides, it occurs to me that if we drive anything into the hole when the water runs out, we shall not be able to get the plug away afterwards.  Then we ourselves could never get here again.”

A long silence followed.  From time to time Masin made a little noise with the drill.

“Perhaps the fellow is asleep,” he observed pleasantly at last.  “So much the better, he will wake in Paradise!”

“It is of no use to run any risks,” said Malipieri.  “If we go down to kill him he may kill one of us first, especially if he has a revolver.  There is no hurry, I tell you.  Do you happen to know how long it takes to starve a man to death?”

“Without water, a man cannot live a week, sir.  That is the best idea you have had yet.”

“Yes.  We will wall him up in the vault.  That is easy enough.  Those boards that are over the shaft will do to make a little frame, and the stones are all here, just as we got them out.  We can fasten up the frame with ends of rope.”

“We have no mortar, sir.”

“Mud will do as well for such a small job,” answered Malipieri.  “We can easily make enough.  Give me your iron, in case he tries to get out, and go and get the boards and the rope.”

Masin began to rise.

“In a week we can come and take him out,” he remarked in a matter-of-fact way.  “By that time he will be dead, and we can have his grave ready.”