Maybe not, but he had just told me something important: that the painting had been retouched with watercolor, which could be easily removed without any damage to the oil painting’s surface. Plus, it could hide anything, including whatever Chaudron might have added to identify his forgeries.

“Is this what you are writing about, the condition of the painting?” he asked. “Every year, someone comes to the Louvre to try and disparage the condition, even the validity of the Mona Lisa. Absurd.”

I told him no, that I just wanted to see it for teaching purposes, and he gave me a look, head tilted, and lips pursed, clearly trying to assess whether or not I was telling the truth. He was about to say something when a young woman entered the gallery.

“Il y a un appel pour vous, Monsieur Gingembre?”

He told her he would be there in a minute, then turned to me. “I must take this call. You have seen enough, yes?”

“No,” I said. “I haven’t even looked at the other paintings in the room.”

Gingembre heaved a sigh and turned toward the young woman. “Marie, see if Gustave is awake and bring him here, and ask Bertrand as well.”

A few minutes later, two guards appeared, one young and burly, the other old and gray.

“Méfiez-vous de lui!” Gingembre said to them.

“I’m sure they will watch me,” I said.

The curator looked surprised and annoyed that I had understood.

“I can only spare the guards for a half hour,” he said, lingering at the edge of the gallery, obviously torn about leaving me with the museum’s greatest work of art, then finally turned to go.

The guards assumed places on either side of the painting, and I took a step closer, my reflection in the glass so like my great-grandfather’s it was startling. I leaned to the side to avoid the glare and study the misty mountains and lakes—the product of Leonardo’s famous sfumato, literally “turned to vapor,” which the artist had produced with thin glazes of linseed oil and pigment painted over and over until edges blurred and the picture took on its otherworldly haze.

What else was veiled? Could Chaudron’s markings have turned to vapor over the years? I slid the magnifying glass from my pocket, and both guards practically pounced.

“Monsieur!”

“I’m not going to touch it,” I said. “I just want to study the brushwork.”

The guards moved in close as I brought the magnifier within a few inches of the painting’s glass and slowly moved it across the surface—every crack and fissure enlarged, strands of Lisa del Giocondo’s hair like rivers and gullies.

“Que cherchez-vous?” the older guard asked.

“Nothing special,” I said, still moving the magnifier inch by inch. In fact, I had no idea what I was looking for—something covered by watercolor or something that had faded away?

The museum was hot and airless, and I felt flushed, the magnifying glass shaking in my hand. “Did you hear that?” I asked the guards.