Moretti eyed the couple too, watched Costa and Peroni walk briskly over to intercept them, then shuffled his coat around him, getting ready to go back to the warmth of his office. He laughed. “Tell your monkeys to be polite, Leo. We’re all watching. Maybe Filippo Viale too. Brave or foolish? When this is over, I suspect we’ll all know which.”

Costa saw them first, brushing past the uniforms on the door with a flash of an ID card and a cocky self-assurance that irked him immediately.

“Hey, Gianni,” he murmured, “you know these people?”

Peroni looked washed out. Teresa had told them to use her place in Tritone when they got a break. There was no way Costa would make it home to the farm on the Appian Way. As for Peroni… Costa could only wonder when the big man had last slept in the small, functional rented apartment he’d found out in the suburbs on the other side of the river, beyond the Vatican. Peroni already had a set of keys to Teresa’s place. Maybe he lived there most of the time anyway.

“No,” Peroni answered, perking up suddenly. He moved quickly to block the couple’s path, holding out his big arms wide, stretching from tape to tape.

The man with the crew cut glowered up at him, half a head shorter but just as big in the body.

“You don’t mind if I ask,” Peroni said. “This isn’t exactly a public performance we’re giving here.”

“FBI,” the American murmured in a low, grunty voice and kept on walking.

“Whoa!” Peroni yelled, and caught the man firmly by the arm, not minding the filthy look he was getting in return.

“Officer,” the female agent said, “this woman is an American citizen.”

“Yeah,” Peroni replied, “I know. But let’s go through some niceties first. My name is Gianni Peroni. This is my partner, Nic Costa. We are policemen. This nice-looking gentleman walking towards us is Inspector Falcone. He’s the boss around here. When he says you get to go further, you go further. Until then-”

Falcone arrived, looked the two FBI agents up and down and said, “Over here we like people to call ahead and make appointments.”

The man withdrew an ID card from his pocket. The woman in the scarlet coat did the same. Costa leaned forward and stared at the photos, checking them, making sure the two Americans understood the point. There were rules here. There were procedures to be followed. She didn’t look much like the photo on the ID card. According to the date it was two years old. She’d seemed much younger then.

“The IDs are fine,” he told them politely. “We have to check. You’d be amazed what the press will do over here just to get a picture.”

“Of course,” the woman answered. She was trying to look like a business executive: expensive, well-cut clothes, blonde hair tied back a little scrappily in a bun that seemed to want to work itself free and let her locks hang more freely around an attractive, almost girlishly innocent face. Something didn’t match up and, just for a moment, he couldn’t stop staring at her. She had razor-sharp, light blue eyes that were cutting into him now.

“I’m Agent Emily Deacon,” she said in perfect Italian. “This-”

She pointed at her colleague without once looking at him and Costa realized, on the instant, she didn’t like the man by her side.

“-is Agent Joel Leapman. We’re here for a reason. If you let us through to see what you’ve got, we just might be able to help.”

Peroni tapped Leapman on the arm and gave him a broad grin. “There. Now that’s asking nicely.”

“So do we get through?” the American snapped.

Falcone nodded, then led the way. Teresa Lupo had cleared the corpse of snow entirely now and indicated to them to wait as she quietly dictated some notes into a voice recorder. The dead woman lay on the geometric slabs, legs and arms akimbo, her white, bloodless skin waxy under the artificial lights. When he’d had the chance between phone calls and working with the SOCOs, Costa had watched closely as the body had emerged from the ice. The positioning of the corpse on the central marble circle was quite deliberate. Her limbs were outstretched, directed at equidistant points in the vast, curving sphere of the Pantheon, as if making a statement. It was an image that jogged a memory and was, perhaps, designed to. He recalled it now. Leonardo da Vinci’s sketch of an idealized figure, a naked man with a full head of hair, set inside first a square then a circle. His limbs described two positions: legs together, at the base of the circle, touching the central arm of the lower side of the square, then apart, on the circle alone; and arms outstretched first horizontally, touching the square alone, then raised, to both the circle and the square’s upper corners.

The dead woman’s stiff position on the shining, damp floor, one surely fixed by her murderer, matched the second of each of these poses perfectly. This was not simply a striking image. It had a meaning, a very specific one.

“The Vitruvian Man,” he said quietly, remembering a distant art lesson from school.

The American woman looked at him oddly. “Excuse me?”

“She reminded me of something. From a long time ago.”

“You’ve got a memory, Mr. Costa,” she conceded. “What else do you recall?”

He tried to flesh out the hazy recollection his brain had dug up from somewhere. It was a long time ago. The idea itself was elusive and complicated too. “That it’s about dimensions and form.” He nodded at the huge spherical roof above them. “Just like this place.”

“Just like this place,” she repeated and, unexpectedly, smiled. The change in expression was remarkable. It took years off her face. She looked like a student suddenly, fresh, unmarked.

It didn’t last. Agent Leapman was making impatient noises. He looked at Teresa Lupo, who was still chanting into the recorder. “You’re the pathologist, right?”

Teresa hit the pause button, blinked and gave him a hard stare. “No, I’m the fucking typist. Just give me a moment and I’ll take your letter next. Who the hell are you, by the way?”

The card got flipped out again as if it were some kind of magic amulet. “FBI.” He nodded at his colleague. “Both of us.”

“Really?” Teresa sighed and went back to talking into the machine.

Quietly, calmly, with a distinct effort designed to cool down the temperature of the conversation, Emily Deacon interposed. “I think we can help.”

The pathologist hit the stop button. “How?”

“She was strangled. With a piece of cord or something. Am I right?”

Teresa glanced at Falcone, searching for a sign. He looked as lost as Peroni and Costa.

“There’s no evidence of sexual assault,” the American woman continued. “This isn’t sexual at all, not in the usual sense anyway. Which begs the question: why did he undress her? It happened here? You do have her clothes?”

“It happened here,” Costa conceded. “Sometime between eight in the evening, when the staff closed the place, and midnight, when we turned up.”

Teresa Lupo was staring at the body again, trying to think. She didn’t stay mad with people for long. Not if she thought they had something she wanted. “It was snowing all last night. All that ice is going to play havoc with everything I normally use for time of death. There are calculations I can use, but they’re not going to be wonderfully accurate in the circumstances.”

The two FBI agents exchanged a glance. It was almost as if they’d seen enough already.

Falcone finally found his voice and Costa couldn’t work out why he’d stayed silent for so long. “I’ve been very generous around here. What do we get in return?”

“We’ll let you know,” Leapman murmured.

Emily Deacon glanced at the pathologist. “This is your call. I’m not trying to push you along. But do you think it would be possible to turn her? I need to see her back.”

Teresa glanced at her assistant Silvio Di Capua, who was putting away some of the equipment they’d been using. Di Capua shrugged.