Fournier tried to maintain his composure, but a corner of his mouth had begun to twitch. “You must be mad!”

“My name is Vincenzo Peruggia, the man convicted of stealing the Mona Lisa, a crime for which I have gone to prison. I am certain you have read about me. I stole the painting for Valfiero, who promised me money. It is a long story and I will not bore you with details, but Valfiero and Chaudron have disappeared, and I must find them. That is why I am here.”

“And what has this to do with me?” Fournier asked, intent upon keeping up his charade.

“Chaudron painted something into each of his forgeries,” Vincent said, “and there are more than one. You are not the only person to have been cheated by this conniving duo. If you let me see the painting, I can prove it.”

“What is this proof you have?”

“Chaudron has put identifying marks into his forgeries.”

“Tell me what kind and I will look for them myself.”

“So you admit to having the painting.”

“I admit no such thing!”

“Monsieur, you would have thrown me out long ago if it were not true. Please, stop wasting my time—and yours—and show me the painting!”

“How do I know you will not simply steal it from me? You, a convicted thief.”

“I have done my time as a thief. All I want now is revenge, and not against you.”

Fournier made him empty his pockets, then searched him for a weapon. All he found was a small jar of turpentine and a swatch of cloth Vincent had brought with him. When he asked why, Vincent told him he would see.

Fournier hesitated a moment, then led him up another staircase and down a long hallway where he tugged an attic staircase from the ceiling. He told Vincent to follow him up the stairs.

Vincent expected the usual dust-filled attic. Instead, it was pristine, with whitewashed walls and a shiny wooden floor. There were four easels with a cloth-covered painting on each. A chair set up in front. Beside it, a small table. On it, a bottle of brandy, a crystal glass, and an ashtray with a half-smoked cigar. It was Fournier’s private viewing room!

Fournier lifted the cloth off the center picture, and there she was, with her knowing eyes and enigmatic smile. For a moment, Vincent wondered if he had made a mistake, if it was indeed Leonardo’s original. He went closer to the painting and took hold of it by its sides.

“What are you doing?” Fournier shouted.

“Turning it over,” Vincent said, and he did, setting the painting back on the easel, upside down. Then he leaned in and squinted at the place just below Lisa del Giocondo’s hands. “There,” he said. “You see those two marks?”

Fournier came in close. “Yes. What are they?”

“Initials. Y and C. For Yves Chaudron. He has signed his painting!” Then he directed Fournier to sniff the painting. “Do you not find it strange that such an old painting still emanates the odor of linseed oil and varnish?” He did not wait for an answer but opened the jar of turpentine he had brought with him and shook a few drops onto the clean cloth. Before Fournier could stop him, he swiped it across a small swath of canvas, then turned the cloth around so Fournier could see it had come away stained with pigment. “Do you think five-hundred-year-old paint comes off so easily? No, monsieur, it does not.”