“Something like that, yes.” Langdon returned his gaze to the text and continued reading aloud.

“Well,” Langdon said, “I’m not sure about headless horses and the bones of the blind, but it sounds like we’re supposed to locate a specific doge.”

“I assume … a doge’s grave?” Sienna asked. “Or a statue or portrait?” Langdon replied. “There haven’t been doges for centuries.”

The doges of Venice were similar to the dukes of the other Italian city-states, and more than a hundred of them had ruled Venice over the course of a thousand years, beginning in A.D. 697. Their lineage had ended in the late eighteenth century with Napoleon’s conquest, but their glory and power still remain subjects of intense fascination for historians.

“As you may know,” Langdon said, “Venice’s two most popular tourist attractions — the Doge’s Palace and St. Mark’s Basilica — were built by the doges, for the doges. Many of them are buried right there.”

“And do you know,” Sienna asked, eyeing the poem, “if there was a doge who was considered to be particularly dangerous?”

Langdon glanced down at the line in question. Seek the treacherous doge of Venice. “None that I know of, but the poem doesn’t use the word ‘dangerous’; it uses the word ‘treacherous.’ There’s a difference, at least in the world of Dante. Treachery is one of the Seven Deadly Sins — the worst of them, actually — punished in the ninth and final ring of hell.”

Treachery, as defined by Dante, was the act of betraying a loved one. History’s most notorious example of the sin had been Judas’s betrayal of his beloved Jesus, an act Dante considered so vile that he had Judas banished to the inferno’s innermost core — a region named Judecca, after its most dishonorable resident.

“Okay,” Ferris said, “so we’re looking for a doge who committed an act of treachery.”

Sienna nodded her agreement. “That will help us limit the list of possibilities.” She paused, eyeing the text. “But this next line … a doge who ‘severed the heads from horses’?” She raised her eyes to Langdon. “Is there a doge who cut off horses’ heads?”

The image Sienna evoked in his mind reminded Langdon of the gruesome scene from The Godfather. “Doesn’t ring a bell. But according to this, he also ‘plucked up the bones of the blind.’ ” He glanced over at Ferris. “Your phone has Internet, right?”

Ferris quickly pulled out his phone and held up his swollen, rashy fingertips. “The buttons might be difficult for me to manage.”

“I’ve got it,” Sienna said, taking his phone. “I’ll run a search for Venetian doges, cross-referenced with headless horses and the bones of the blind.” She began typing rapidly on the tiny keyboard.

Langdon skimmed the poem another time, and then continued reading aloud.

“I’ve never heard of a mouseion,” Ferris said.

“It’s an ancient word meaning a temple protected by muses,” Langdon replied. “In the days of the early Greeks, a mouseion was a place where the enlightened gathered to share ideas, and discuss literature, music, and art. The first mouseion was built by Ptolemy at the Library of Alexandria centuries before the birth of Christ, and then hundreds more cropped up around the world.”

“Dr. Brooks,” Ferris said, glancing hopefully at Sienna. “Can you look and see if there’s a mouseion in Venice?”

“Actually there are dozens of them,” Langdon said with a playful smile. “Now they’re called museums.”

“Ahhh …” Ferris replied. “I guess we’ll have to cast a wider net.” Sienna kept typing into the phone, having no trouble multitasking as she calmly took inventory. “Okay, so we’re looking for a museum where we can find a doge who severed the heads from horses and plucked up the bones of the blind. Robert, is there a particular museum that might be a good place to look?”

Langdon was already considering all of Venice’s best-known museums — the Gallerie dell’Accademia, the Ca’ Rezzonico, the Palazzo Grassi, the Peggy Guggenheim Collection, the Museo Correr — but none of them seemed to fit the description.

He glanced back at the text.

Kneel within the gilded mouseion of holy wisdom …

Langdon smiled wryly. “Venice does have one museum that perfectly qualifies as a ‘gilded mouseion of holy wisdom.’ ”

Both Ferris and Sienna looked at him expectantly.

“St. Mark’s Basilica,” he declared. “The largest church in Venice.”

Ferris looked uncertain. “The church is a museum?”

Langdon nodded. “Much like the Vatican Museum. And what’s more, the interior of St. Mark’s is famous for being adorned, in its entirety, in solid gold tiles.”

“A gilded mouseion,” Sienna said, sounding genuinely excited.

Langdon nodded, having no doubt that St. Mark’s was the gilded temple referenced in the poem. For centuries, the Venetians had called St. Mark’s La Chiesa d’Oro — the Church of Gold — and Langdon considered its interior the most dazzling of any church in the world.

“The poem says to ‘kneel’ there,” Ferris added. “And a church is a logical place to kneel.”

Sienna was typing furiously again. “I’ll add St. Mark’s to the search. That must be where we need to look for the doge.”

Langdon knew they would find no shortage of doges in St. Mark’s — which was, quite literally, the basilica of the doges. He felt encouraged as he returned his eyes to the poem.

Trickling water? Langdon wondered. Is there water under St. Mark’s? The question, he realized, was foolish. There was water under the entire city. Every building in Venice was slowly sinking and leaking. Langdon pictured the basilica and tried to imagine where inside one might kneel to listen for trickling water. And once we hear it … what do we do?

Langdon returned to the poem and finished reading aloud.

“Okay,” Langdon said, disturbed by the image, “apparently, we follow the sounds of trickling water … to some kind of sunken palace.”

Ferris scratched at his face, looking unnerved. “What’s a chthonic monster?”

“Subterranean,” Sienna offered, her fingers still working the phone. “ ‘Chthonic’ means ‘beneath the earth.’ ”

“Partly, yes,” Langdon said. “Although the word has a further historic implication — one commonly associated with myths and monsters. Chthonics are an entire category of mythical gods and monsters — Erinyes, Hecate, and Medusa, for example. They’re called chthonics because they reside in the underworld and are associated with hell.” Langdon paused. “Historically, they emerge from the earth and come aboveground to wreak havoc in the human world.”

There was a long silence, and Langdon sensed they were all thinking the same thing. This chthonic monster … could only be Zobrist’s plague.