Still feeling a bit shaky, I ducked into a tabac, perused the candy, chose something called Arlequin, in a garish multicolored bag. The hard candies were individually wrapped, which led me to believe they’d be more upscale than their artificial tutti-frutti supersweet flavor turned out to be.

I’d eaten three by the time I found 67 rue de Perche, an old three-story townhouse. I raised a bronze knocker in the shape of a lion’s head and let it fall back.

The man who opened the door was wearing a blue satin robe, in his late forties, tall and striking. “Qu’est-ce que c’est?” he asked, his tone clipped and cool.

“Étienne Chaudron?” I asked.

He nodded.

“I’m Luke Perrone. We spoke on the phone—”

He took a minute to figure out who I was, and when he did, he didn’t look happy. “I was perfectly clear that I have nothing to say to you.”

“Yes, but I was in Paris and…” I quickly spoke the lines I’d rehearsed. “I’ve been reading Vincenzo Peruggia’s diary, and your great-uncle, Yves, plays a major part in it. I have something important to discuss with you.”

“And what could that possibly be?”

“May I come in? I promise not to take much of your time.”

He opened the door reluctantly, and I followed him through a foyer with a decorative relief of unfurling ribbons just below the ceiling, obviously old, some of the plasterwork cracking, but still lovely. Several suitcases were lined up, and I asked if he was going away.

“A short vacation—the south of France,” he said, leading me past a winding wooden staircase with a beautifully curved banister into a small sitting room with a marble fireplace, a crystal chandelier, built-in bookcases, and two comfy leather sofas. He indicated I should sit, though he remained standing, so I stood too.

“What is it you have to say that is so important?”

“I believe Yves Chaudron was in league with my great-grandfather, Vincenzo Peruggia, to steal the Mona Lisa.”

“And?”

“That doesn’t surprise you?”

“I have heard it before, many times.”

“Peruggia’s diary clearly states that your great-uncle painted several versions of the Mona Lisa during its two-year absence from the Louvre.”

He sighed. “Every year, I hear another story about my infamous great-uncle and the forgeries he supposedly made, but there is never any proof they were made by my great-uncle’s hand.”

“That’s exactly what I’m looking for—proof. A way to distinguish your great-uncle’s forgeries.”

Étienne Chaudron raked a hand through his hair and took a breath. “Even if the forgeries did exist, there would be no way to prove it.”

“According to the journal, your great-uncle switched paintings on Peruggia, so it was one of his forgeries that was returned to the Louvre.”

“Monsieur Perrone…” Chaudron shook his head and sighed again. “If that were true, it would be a marvelous hoax, but I have no idea about such a thing.”

“Why would Peruggia make it up?”

“You seriously ask such a question about the man who stole the world’s most famous painting? Have you not considered qu’il était fou?”