The footsteps tipped him off. The hooded man paused along the cobblestones and whirled. His fingers closed on the garments of the ragged youth who had been following him and flung the boy against the wall of the nearest palazzo.

It was night, and the lanes of this particular rione of Rome were remarkably silent. The hooded man had to squint to make out the lad’s face.

“Signor,” the boy said, “I beg your—” His breath froze when the tip of a dagger came to rest under his right eyeball.

“You were saying?” said the hooded man.

“I meant you no harm, Signor.”

“Drop it. Drop it now, or your eye hits the ground first.”

The youth unclenched his left hand. A stout club fell to the stones with a thunk. The hooded man eased a breath from his lungs. “I seek Baldani,” he said. “I’m told he lives in this quarter.”

“What, the learned man? The doctor?”

The hooded man waggled his head, as if unwilling to concede either point. “Doctor? Ha. Where?”

The youth pointed with his eyes. “That way. Three doors down. This side. Want me to take you?”

“I want you to go. And if I ever see you again on the same street where I am passing, I’ll take it as permission to—”

He lowered the blade to the boy’s throat.

“No, Signor.”

“Vattene!”

He let the boy slide down the wall. “Go,” he repeated. “Leave the cudgel.”

The boy scurried away. The hooded man paused to catch his breath. He was sixty, a youth no longer. He studied the boy’s club a moment before kicking it away. An effective weapon, perhaps, he thought. But a tool for amateurs. He slid his short blade back into its sheath, which he wore at his wrist.

He adjusted his garments and proceeded to the address. The tan stucco structure stunk of fish and a damp, smoky fire. He took the stairs two at a time to arrive at the top apartment.

An open door. One of his brother’s thugs, a former soldier, waited on the landing. He shifted his partizan and brought his heels together.

“Your Eminence.”

“Go,” said the hooded man.

The guard descended.

Two men waited inside. A gaunt wastrel in his forties, dressed in once-fine clothes, and another guardsman.

“Leave us,” the hooded man said.

The guard slinked away.

The hooded man scanned the room. A low table near the window was cluttered with glassware, a pair of mortars and pestles, small candles burnt low, some iron filings in a cup, and numerous items culled from nature. The papery remains of a wasp’s nest, and a dead bird. 

A bed and washstand in the corner were the only signs that someone lived in the squalid flat. The rest of the apartment was cluttered with books, most of which were stacked on the floor amid dust and cobwebs.

The man settled into the largest chair, hoping to take advantage of the prestige it afforded him. He pulled back his hood. On his head he wore a crimson zucchetto, the skullcap marking him as a prince of the Church.

“Uncle,” Baldani said, “is this really necessary? I can explain any hint—”

The cardinal lifted a finger.

Baldani shushed.

The cardinal withdrew a small roll of parchment from his robes. 

 “It has come to the attention of several in the family that you have been performing … indulging … yourself in bizarre activities which display an outright disrespect for life and are in obvious violation of Church teaching.”

A dirty felt cap covered Baldani’s bald head. His stained fingertips twitched. “I can’t think to what this refers. I have no wish to go against Church teaching, Uncle.”

“You’ll address me as Your Eminence or Cardinal Farnese. In this matter I do not wish to be reminded of my late sister or the scoundrel she once called husband. Proceed.”

“Very well, Your Eminence,” the younger man said, clearing his throat. “I take it this refers to my da Vinci experiment, then?”