Although she had questioned her father on the subject and listened carefully to his answers, Potitia could not quite understand whether the amulet actually was Fascinus, or contained Fascinus, or only represented Fascinus, in the way that the idols of the Phoenicians were said to represent their gods. Despite her lack of clear understanding, Potitia nonetheless felt very grown-up when she wore the amulet. She was no longer the girl with skinned knees and muddy feet, the child who wandered carefree across the little world of the ruma. Even so, she carried within her a child’s sense of wonder and the sweet nostalgia of having grown up in a world where there was little to fear and much to discover.

Until very recently, that world had remained unchanged-a place where strangers met in good company and where Potitia might expect to raise her own children with little concern for their safety, allowing them to wander at will, as she had done. But now, all that had changed. The world had become dark and dangerous. Families kept their children always in sight. Even grown men did not dare to wander alone across the ruma.

The coming of the monster Cacus had changed everything.

It was Potitia who had seen him first, that day she headed down to the river to wash a basket of clothes. At the sight of him, she screamed, dropped the basket, and fled. The creature ran after her, making a hideous noise that made the hair rise on the back of Potitia’s neck: “Cacus! Cacus!”

Just when her energy flagged and he might have caught her, the monster gave up the chase. Potitia reached the settlement unharmed. She was convinced that Fascinus, and Fascinus alone, had saved her. All the way back to the village, she ran with one hand at her throat, grasping the amulet tightly, begging for Fascinus’s protection, whispering aloud, “Save me! Save me, Fascinus!” Afterward, trembling with relief, she whispered again to the amulet, giving it her thanks and pledging her devotion. It was a prayer that Potitia uttered, in just such a manner as the Phoenicians would have understood, made not to a nameless numen that inhabited a thing or place, but to a powerful, superhuman entity that possessed the intelligence to understand her words. She had not offered ritual propitiation to a numen, but had prayed directly to a god. In that moment, although Potitia acted with no idea of the significance of what she had done, Fascinus became the first native god to be worshiped in the land of the ruma.

For a long time, no one but Potitia had seen the monster, and there were those in the settlement, listening to her description of Cacus, who thought that she must have imagined the encounter on the path. Her family, after all, were known for their fanciful beliefs, showing off the amulet they called Fascinus and hinting that their line had sprung from the union of a numen and a woman-as if such a thing were possible!

Then, little by little, it became evident that some malicious creature was indeed among them. Bits of food went missing, along with small objects that no one had cause to steal. Now and again, objects of value were found broken-a spinning wheel, a clay pot, a toy wagon made of wood-as if some overgrown, immensely strong child smashed them out of spite. The troublemaker struck at night and left no trail; Cacus had grown skillful at covering his tracks.

The settlers were angry and frightened. Their fear of the monster was compounded by another: that the traders who came to the market would learn about Cacus and be frightened away. If traders stopped coming, the settlers would lose their livelihood, and the settlement might vanish altogether.

One morning, during the busiest cattle market of the year, everyone in the settlement was awakened by a lowing among the cattle. Outside the pen, a cow was found dead, its body torn open and much of the flesh missing. The cow could not have climbed over the fence, and the gate remained shut. What sort of man could possess the strength to lift a cow up and over the rough-hewn fence, and then to kill the beast and tear it open with his bare hands? A thrill of panic ran through the settlement. Some of the cattle-traders rounded up their herds and drove them homeward at once.

Armed with knives and spears, hunting in pairs, the settlers combed the Seven Hills. Two of the hunters must have found the monster. Their bodies were eventually discovered on the hill of the osier trees, broken and eviscerated, much as the cow’s body had been.

It did not take long for word to spread up and down the trails that led to the ruma: The monster that was stalking the trading post had an appetite for human flesh. Traders did not merely stop doing business at the settlement; they made great detours to avoid passing anywhere near it.

With most of the traders gone and traffic so greatly reduced on the trails, the monster grew even bolder. An infant went missing. Her remains were found only a short distance from the settlement, at the foot of the steep hill on the far side of the Spinon. One of the searchers, looking up to avert his eyes from the horrible sight, glimpsed a movement on the hillside above. From behind a bramble-covered lip of stone, a hideous face peered down for a moment, then disappeared. A moment later, a shower of rocks rained down on the searchers, who fled. Peering up at the hillside from a safe distance, they discerned what appeared to be a cave, its opening obscured by brambles. None of them could see a way to scale the hillside. Even if it could be scaled, none of them could imagine what would await them once they reached the mouth of the cave.

Back at the settlement, the searchers told what they had discovered. To her horror, Potitia realized that the monster had taken up residence in her secret cave, which was a secret no longer.

From his hole high up in the side of the hill, Cacus ventured out at night to terrorize the settlement. During the day, he stayed hidden in the cave.

More than once, the settlers attempted to scale the hillside and attack him in his lair. Bellowing his name, Cacus dropped stones on them. One settler fell and broke his neck. Another was struck in the eye and blinded. Another managed to draw closer to the mouth of the cave than anyone else, but was killed instantly by a stone that struck his forehead. Instead of falling, his limp body became caught on sharp rocks and brambles. No one dared to climb up and retrieve it. There it hung for several days and nights, a horrifying rebuke to those who had sought to destroy the monster. One morning, the body was no longer there. Cacus had claimed it. The man’s bones, picked clean, appeared one by one at the foot of the hill as Cacus tossed them out.

It was Potitius who suggested that the hillside be set afire. If the flames and smoke did not kill the monster outright, they might at least drive him from his lair. The brambles at the foot of the hill were set on fire. The flames spread upward, heading directly for the cave. Then a wind blew up from the Tiber and drove the flame this way and that. Embers spiraled high in the air, blew across the Spinon, and ignited the thatched roof of a hut. The flames spread from hut to hut. The settlers worked desperately to douse the flames with buckets of water from the river. When the fire at last burned itself out, the face of the hillside was scorched and black, but the cave was untouched and the monster unharmed.

It was decided that a watch should be set upon the cave, so that, if the monster descended, an alarm could be raised. Men and boys took turns throughout the day and night, training their eyes upon what little could be seen of the mouth of the cave from below.

One of Potitia’s cousins, a burly, hotheaded youth named Pinarius, boasted to her that he would put an end to Cacus once and for all. Caught up in his enthusiasm, Potitia confessed to her cousin that she had climbed to the cave many times. Scarcely believing her, Pinarius nonetheless accepted her explanation of how it could be done.