"We have with us one who is familiar with every nook in the city of Rome," the Prefect turned to the Cardinal-Archbishop of Ravenna. "Long have we suspected that all is not well in the deserted pavilion. But though we watched by day and by night nothing seemed to reward our efforts, until one stormy night a dreadful shape with the face of a devil came forth, and the sight so paralyzed those who watched from afar that they fled in dismay, believing it was the Evil One in person who had come forth from the bowels of the earth. From yonder door a dark corridor leads to a shaft whence it winds in a slight incline into the devil's chapel below. The latter is so situated that we can watch these outcasts at their devotions, unseen, our presence unguessed. This way! Let silence be the password. Keep in touch with each other, for the darkness is as that of the grave." A flash of lightning that seemed to rend the very heavens enveloped them for a moment in its sulphureous glare, followed by a crash of thunder that shook the very earth. The hurricane shrieked, and the rain came down in torrents. They had advanced to the very edge of the underbrush, stumbling over the heads and torsos of broken statues that lay among parasitic herbage. Monstrous decaying leaves curled upward, leprous in the lightnings. A poison mist seemed to hover over this lonely and deserted pleasure-house of ancient Pelasgian days. Skirting the haunted pavilion, unmindful of the onslaught of the elements, they took a path so narrow that they could but advance in single file. This path had been cut and beaten by the Prefect's guards, for the weeds and underbrush luxuriated, until they mounted some ten feet against the walls of the pavilion. They had now reached the back wall and proceeded in utter darkness broken only by the flashes of lightning. They passed through a half-ruined archway and at last came to a halt, prompted by those in front, whose progress had been stopped by, what the others guessed to be, the door. They had to work warily, to keep it from falling inward. At last the movement continued and they entered the night-wrapt corridor. Tristan had taken his station directly behind the Prefect of Rome. The ecclesiastics, for their own protection, had been assigned the rear. By the sheen of lightnings a pile of brushwood was revealed to the sight, which the Prefect, in a low tone, ordered to be cleared away, whereupon a circular opening appeared, like the entrance of a well. The Prefect summoned the leaders around him. For a moment they stood in silence and listened. Between the peals of the thunder which rolled in terrifying echoes over the Seven Hills, the trained ear could distinguish a strange, droning sound that seemed to come from the bowels of the earth. "Even now the Black Mass is commencing," he turned to Tristan. "We are but just in time." After a pause he continued: