Through the better part of two days, his fever builds, dropping only to rise again. More bleeding, more leeches. The Duchess tears up more sheets for lint, changes more dressings. Holds a damp towel to Charles' brow, meets his wildest ravings with a raspy coo. She doesn't even f linch when, late in the second day, he sings-three times-the ditty with which he favored our Palais-Royal prostitutes.

Mainly, though, his repertoire consists of groans and wails. One night, a particularly strenuous cry jars me from my cot, sends me f lying toward his bed, where I'm astonished to find him, for once, in a deep sleep. A second later, an even louder cry rends the darkness.

Lighting a lamp, I creep into the hallway. The door to Vidocq's bedroom stands open about a foot, and in the aperture I see the satiated face of Jeanne-Victoire, sprawled naked across the bed. Driving into her from behind: the great Vidocq, mossy-chested and omnivorous, a deity in human form.

I'm too astonished to look away-or even conceal myself. In a voice decidedly suave, Vidocq drawls:

"Close the door, will you, old boy?"

The next morning, he comes down to f ind me picking at an omelette of chives and cheese. When he asks me how the patient is, I answer in two words, and I decline to meet his eye.

"Ohh," he says. "Sulking, are we? I didn't realize I needed your say-so to fuck a woman in my own bed."

"She's not just any woman."

"That's the truth," he answers, exploding into a grin.

I slide him a bowl of cream for his coffee. Toss him a napkin.

"Just promise me one thing," I say.

"Name it."

"You'll do right by her child."

"Child? "

"The baby. The one we found in Poulain's apartment."

He stares at me. "The baby died of smallpox, Hector. Not ten days after we saw her."

"But she-no, Jeanne-Victoire said the child was staying with her brother. In Issy."

"Well, yes, that's where they're both buried. I should know, I paid the expenses. Oh, come, don't look like that. Jeanne-Victoire's made of tougher stuff than either of us. She'll get through."

It f lashes across my mind now: her face as I saw it that night in the alleyway, standing over Herbaux's crumpled form. Small white teeth shining in the moonlight. A feral prettiness. Still very much with the living.

"The question," says Vidocq, dropping his head into his hands, "is will I get through?"

Th at e vening, ins tead of retiring to my cot, I fall asleep in my chair. A comprehensive sleep, dreamless, trackless. The next morning, Mama Vidocq has to shake me a good five minutes before she can wake me.

"Doctor," she says. "The fever's broken."

An hour later, when the Duchess arrives, Charles is, for the first time in his convalescence, sitting up in bed. A potted geranium rests in his lap. Orange pulp shines from the crevices of his teeth. His eyes are a Persian blue.

"Good morning, Marie."

She lowers herself onto his bed. Takes his palm and presses her forehead against it.

"I can sca rce ly believe it," she tells me later that morning. "He's his old self. . . ."

How strangely the phrase sounds on her lips. His old self. A man she's known but two weeks. A boy she last saw twenty-four years ago.

She and I are sitting in Vidocq's salon, taking coffee-which her state of mind has rendered her incapable of drinking. She raises the cup . . . lets it fall. Again and again, her very own Tantalus.

"Curious," she says. "My brother remembers virtually nothing of the scaffold or the guillotine, but he does recall what happened along the way. He said you made him-go to sleep somehow. Without actually going to sleep. Oh, he was very confused about it, but he was quite clear on one point."

"Yes ?"

"You saved his life."

Fragments of self-deprecation form in my throat . . . but she frees

me of the need to use them.

"Tell me what you did," she says.

I have held out all this time without discussing my research-with

anyone. But now, under great caution, I raise the name of Mesmer. A Viennese physician who blew into Paris forty years ago on clouds of scandal, expounding a theory called "animal magnetism." Working with the most hopeless medical cases, Mesmer attached magnets to their bodies, waved a wand in front of them-and somehow effected remarkable cures.

Traditional physicians loathed him, and after the Faculty of Medicine declared him a fraud, Mesmer slouched home. The cures themselves were hard to overlook, and there arose a clique of Parisian scientists who believed that Mesmer's therapeutics might be detached from his dubious physics.

I was one of them. Having witnessed the effects of altered consciousness in a clinical setting, I came to believe that these same techniques could be used to reduce vascular f low. If so, then Mesmer's once-discredited practices might one day have revolutionary impacts on surgery and on the treatment of traumatic injuries.

The Duchess, I will give her this, listens to the whole business without a yawn or a drooping lid. Only when she's certain I'm done talking does she ask: "How does one prove such a theory, Doctor? If there aren't any dying men at hand."