Moving up the hill now, her sturdy sandals slapping against griddle-hot stones, she walked past the Sanctuary and House of Saint Catherine, the patron saint of Siena, who had survived for long periods on no other food but the Blessed Sacrament. Saint Catherine had experienced vivid visions of Hell and Purgatory and Heaven, and had lusted for the glory and divine agony of martyrdom. After a long and uncomfortable illness, all she’d managed was a disappointingly ordinary death. As Lily labored up the hill, she thought: I have seen visions of Hell, too. But I want no part of martyrdom. I want to live. I’ll do anything to live.

By the time she climbed to the Basilica di San Domenico, her T-shirt was soaked with sweat. She stood panting at the top of the hill, gazing down upon the city, its tiled roofs blurred to soft focus in the summery haze. It was a view that made her heart ache, because she knew she would have to leave it. Already she’d lingered in Siena longer than she should have, and she could now feel the evil catching up to her, could almost smell its faint, foul odor wafting in on the wind. All around her, doughy-thighed tourists swarmed the hilltop, but she stood in silent isolation, a ghost among the living. Already dead, she thought. For me, this is borrowed time.

“Excuse me, Miss? Do you speak English?”

Startled, Lily turned to see a middle-aged man and woman wearing matching U Penn T-shirts and baggy shorts. The man was clutching a complicated-looking camera.

“Do you want me to take your picture?” Lily asked.

“That’d be great! Thanks.”

Lily took the camera. “Is there a trick to this one?”

“No, just press the button.”

The couple linked arms and posed with the view of Siena stretching like a medieval tapestry behind them. Their souvenir of a strenuous climb on a hot day.

“You’re American, aren’t you?” said the woman as Lily handed back the camera. “So where are you from?” It was merely a friendly question, something countless tourists asked each other, a way to connect with fellow travelers far from home. Instantly it put Lily on guard. Their curiosity is almost certainly innocent. But I don’t know these people. I can’t be certain.

“ Oregon,” she lied.

“Really? Our son lives there! Which city?”

“ Portland.”

“Now, isn’t it a small world? He lives on Northwest Irving Street. Is that anywhere near you?”

“No.” Already Lily was backing away, retreating from these overbearing people who would probably next insist that she join them for coffee, and ask her ever more questions, probing for details she had no intention of sharing. “Have a nice visit!”

“Say, would you like to-”

“I have to meet someone.” She gave a wave and fled. The doors of the basilica loomed ahead, offering sanctuary. She stepped inside, into cool silence, and breathed a sigh of relief. The church was nearly empty; only a few tourists wandered the vast space, and their voices were blessedly hushed. She walked toward the Gothic arch, where the sun glowed through stained glass in chips of jeweled light, past the tombs of Sienese nobles that lined both walls. Turning into a chapel niche, she stopped before the gilded marble altar and stared at the tabernacle containing the preserved head of Saint Catherine of Siena. Her mortal remains had been divided and distributed as holy relics, her body in Rome, her foot in Venice. Had she known this would be her fate? That her head would be wrenched from her decaying torso, her mummified face displayed to countless sweaty tourists and chattering schoolchildren?

The saint’s leathery eye sockets gazed back from behind glass. This is what death looks like. But you already know, don’t you, Lily Saul?

Shivering, Lily left the chapel niche and hurried through the echoing church, back toward the exit. Outside again, she was almost grateful for the heat. But not for the tourists. So many strangers with cameras. Any one of them might be furtively snapping her photo.

She left the basilica and started back downhill, through the Piazza Salimbeni, past the Palazzo Tolomei. The tangle of narrow streets easily befuddled tourists, but Lily knew the way through the maze, and she walked quickly, purposefully, toward her destination. She was late now, because she’d lingered too long on the hill, and Giorgio would surely scold her. Not that the prospect offered any sort of terror, for Giorgio’s grumblings never resulted in consequences of any significance.

So when she arrived at work fifteen minutes late, she did not feel even a hint of trepidation. The little bell tinkled on the door, announcing her entrance as she stepped into the shop, and she inhaled the familiar scents of dusty books and camphor and cigarette smoke. Giorgio and his son, Paolo, were hunched over a desk near the back of the shop, both of them wearing magnifying loupes around their heads. When Paolo looked up, one enormous eye stared like a cyclops at Lily.

“You must see this!” he called out to her in Italian. “It just arrived. Sent by a collector from Israel.”

They were so excited, they hadn’t even noticed she was late. She set her backpack down behind her desk and squeezed her way past the antique table and the oak monastery bench. Past the Roman sarcophagus, which now served ignominiously as a temporary container for file storage. She stepped over an open crate that had spilled wooden packing shavings onto the floor, and frowned at the object on Giorgio’s desk. It was a block of carved marble, perhaps part of an edifice. She noticed the patina on two adjoining surfaces, a soft gleam left by centuries of exposure to wind and rain and sun. It was a cornerstone.

Young Paolo pulled off his loupe, and his dark hair stood up. Grinning at her with those earlike tufts of hair, he looked like one of the legendary Sienese werewolves, albeit a perfectly harmless and utterly charming one. Like his father, Paolo possessed not a single ounce of cruelty, and were it not for the fact that she would inevitably be forced to break his heart, Lily would happily have taken him as a lover.

“I think you will like this piece,” he said, and offered her his magnifier. “It is just the sort of thing you’re always interested in.”

She bent over the cornerstone and studied the manlike figure carved there. It was standing upright, with a skirt around its waist and decorative bracelets and anklets. But the head was not human. She slid the magnifier over her head and leaned in closer. As the details came alive through the lens, she felt a sudden chill. She saw jutting canine teeth and fingers tipped with claws. And horns.

She straightened, her throat dry, her voice oddly distant. “You said the collector is from Israel?”

Giorgio nodded and took off his loupe, revealing an older, plumper version of Paolo. The same dark eyes, but webbed with laugh lines. “This man is new to us. So we’re not sure of the provenance. Whether to trust him.”

“How did he happen to send us this piece?”

Giorgio shrugged. “It arrived in the crate today. That’s all I know.”

“He wants you to sell it for him?”

“He asked only for an appraisal. What do you think?”

She rubbed a finger across the patina. Felt the chill again, seeping from the stone to her flesh. “Where does he say it comes from?”

Giorgio reached for a bundle of papers. “He says he acquired it eight years ago, in Tehran. I think it must be smuggled.” He gave another shrug, a wink. “But what do we know, eh?”

“Persian,” she murmured. “This is Ahriman.”

“What is Ahriman?” asked Paolo.

“Not a what, a who. In ancient Persia, Ahriman is a demon. The spirit of destruction.” She set the magnifier on the desk and took a deep breath. “He’s their personification of evil.”

Giorgio gave a laugh and rubbed his hands in glee. “You see, Paolo? I told you she’d know. Devils, demons, she knows them all. Every time, she has the answer.”