The Prefect of Rome bent forward and inserted a gleaming piece of steel in the keyhole. After a wrench or two, which convinced the onlookers that the door had been long in disuse, it swung inward with a groan. The Prefect, with a muttered imprecation, beckoned his followers to enter, and when they were assembled in what appeared to be a courtyard, he took pains to close the door himself, to avoid the least noise that might reach the ear of those within the enclosure. At the far end of this courtyard a shadowy pavilion arose, culled from the Stygian gloom by the sheen of the lightnings. It seemed to have been erected in remote antiquity. A circular structure of considerable extent, its ruinous exterior revealed traces of Etruscan architecture. No one dared set foot in it, for it was rumored to be the abode of evil spirits. Its interior was reported to be a network of intricate galleries, leading into subterranean chambers, secret and secluded places into which human foot never strayed, for, not unlike the catacombs, it was well-nigh impossible to find the exit from its labyrinthine passages without the saving thread of Ariadné. At a signal from the Prefect of the Camera all stopped. Heavy drops of rain were falling. The hurricane increased in fury. It was a weird scene and one the memory of which lingered long after that eventful night with Tristan. Black cypresses and holm-oaks formed a dense wall around the pavilion on two sides. In the distance the white limbs of some pagan statues could be seen gleaming through the dark foliage. And, as from a subterranean cavern, a distant droning chant struck the ear now and then with fateful import. Now the Prefect of Rome threw off his cloak. The others did likewise. Their masks they retained. "There is a secret entrance, unknown even to these spawns of hell, behind the pavilion," he addressed his companions in a subdued tone, hardly audible in the shrieking of the storm. "It is concealed among tall weeds and has long been in disuse. The door is almost invisible and they think themselves safe in the performance of their iniquities below." "How can we reach this pit of hell?" Tristan, quivering with ill-repressed excitement interposed at this juncture. He could hardly restrain himself. On every moment hung the life of the being dearer to him than all the world, and he chafed under the restraint like a restive steed. If they should be too late, even now! But the Prefect retained his calm demeanor knowing what was at stake. It was not enough to locate the chapel of Satan. Those participating in the unholy rites must not be given the chance to escape. They must be taken, dead or alive, to the last man.