The last resource was the porter at the outer gate.  They applied to him; and in answer to their questions he asserted that he had most certainly seen a lady in a yellow domino and mask drive away, about half an hour before, in a hired coach.

“Should you remember the coachman again?” asked D’Arbino.

“Perfectly; he is an old friend of mine.”

“And you know where he lives?”

“Yes; as well as I know where I do.”

“Any reward you like, if you can get somebody to mind your lodge, and can take us to that house.”

In a few minutes they were following the porter through the dark, silent streets.  “We had better try the stables first,” said the man.  “My friend, the coachman, will hardly have had time to do more than set the lady down.  We shall most likely catch him just putting up his horses.”

The porter turned out to be right.  On entering the stable-yard, they found that the empty coach had just driven into it.

“You have been taking home a lady in a yellow domino from the masquerade?” said D’Arbino, putting some money into the coachman’s hand.

“Yes, sir; I was engaged by that lady for the evening—­engaged to drive her to the ball as well as to drive her home.”

“Where did you take her from?”

“From a very extraordinary place—­from the gate of the Campo Santo burial-ground.”

During this colloquy, Finello and D’Arbino had been standing with Fabio between them, each giving him an arm.  The instant the last answer was given, he reeled back with a cry of horror.

“Where have you taken her to now?” asked D’Arbino.  He looked about him nervously as he put the question, and spoke for the first time in a whisper.

“To the Campo Santo again,” said the coachman.

Fabio suddenly drew his arms out of the arms of his friends, and sank to his knees on the ground, hiding his face.  From some broken ejaculations which escaped him, it seemed as if he dreaded that his senses were leaving him, and that he was praying to be preserved in his right mind.

“Why is he so violently agitated?” said Finello, eagerly, to his friend.

“Hush!” returned the other.  “You heard him say that when he saw the face behind the yellow mask, it was the face of his dead wife?”

“Yes.  But what then?”

“His wife was buried in the Campo Santo.”

CHAPTER V.

Of all the persons who had been present, in any capacity, at the Marquis Melani’s ball, the earliest riser on the morning after it was Nanina.  The agitation produced by the strange events in which she had been concerned destroyed the very idea of sleep.  Through the hours of darkness she could not even close her eyes; and, as soon as the new day broke, she rose to breathe the early morning air at her window, and to think in perfect tranquillity over all that had passed since she entered the Melani Palace to wait on the guests at the masquerade.