The first thing I see is the high-crowned hat. Moving downward: a dandyish, outsize collar, an even larger necktie. Three waistcoats, worn one over the other, each a different shade of olive. A short-waisted fishtail coat and a double row of silver buttons marching straight up a rather prosperous belly.

"Eats well," says Vidocq, sourly. "Hold on. Who's that behind him, Hector? "

An apron with a dusty-rose border billows into the doorframe, pursued by a single chapped hand.

"It's the cook, I think."

Tepac turns his head back, lifts his hand in farewell. Then, from the interior of the house, comes another figure: the man-of-all-work, striding past with a kettle full of wood chips. He angles his chin toward Tepac and disappears round the side of the house.

The briefest of tableaus, yes, but enough to give me a sense of . . . easy terms, I suppose . . . domestic covenants, lightly shouldered. This fellow may take airs with his townsmen, but in his own castle, he wears the master's robes lightly.

Giving his oaken staff a rapier twirl, Monsieur Tepac sets off down the road, in the general direction of the river.

"After you," whispers Vidocq. "After you, my highliness."

CHAPTE R 2 0.

In Which Tourism Is Shown to Be Hazardous Quick ly Vidocq lay s out the parameters. Two of us will follow Tepac; the third will circle round and rejoin the party after five minutes; the first man will then peel off, and the rotation will continue.

Always we stay in conversation with one another. Under no circumstance do we make eye contact with the quarry. Periodically, we step aside to make small changes in our appearance: adding a scarf, dropping a tie, turning a vest inside out. Vidocq, during one changeover, slaps on a pair of leather gaiters, and a short while later, Goury appears in a red Phrygian bonnet that was last seen on the Bastille ramparts.

What would Monsieur Tepac think, I wonder, if he knew how much effort was being expended on his behalf? But he never looks back, never even moves his head as he keeps his course through SaintCloud's half-deserted streets. To the people who pass-a tinman, an umbrella peddler, an old woman cadging for change-he pays not the slightest heed.

"Even Bonaparte would have given 'em a fucking nod," grumbles Vidocq.

We follow him over a brook, through a copse of sycamores, over blankets of moss and a sward of Henry the Fourth's ruff. For entire intervals, Monsieur Tepac's stout figure disappears entirely from view, only to reappear in some unexpected place, like the cleft in a linden.

A half hour more, and he is veering south. No curlicues this time. He walks with greater purpose, as if a destination has suddenly occurred to him. And as the Seine breaks once more onto our eye, and the stone bridge rears up on our left, I realize, with a sting of something like hilarity, where he's heading.

"Oh, the bastard! " says Vidocq.

Th e King of France's park is still a grand place to visit in these early days of the Restoration. Most people make a point of going in the summer, when, on any given Sunday, twenty-four jets of water come blazing into life. There's always a watercolorist with an easel propped under an old chestnut, and there's always a band playing, and complete strangers dance together in the high damp grass.

On a Tuesday in April, however . . . well, the chateau is closed, and there are maybe a dozen and a half people strolling through the grass and bindweed-most of them English missionary ladies in black fender-bonnets. The waterworks are on hold. Le Notre's great parterres de broderie are no more than boxwood skeletons.

The birds are here, though, threshing the lawns. And the air, that's here, too. Even Monsieur Tepac pauses alongside the carp basin to take his fill of it.

Is i t now that I remember? That it was the same air beloved of Marie-Antoinette?

She tasted it, yes, and resolved that the air of Saint-Cloud was fit for royal children to breathe. And so, at her behest, the King bought the chateau from his cousin, and this became the royal family's haven from the Parisians who stared daggers at them through the long days and nights.

It was Saint-Cloud they were trying to reach before everything fell apart. April 18, 1791: The royal berline came thundering out of the Tuileries courtyard, bound on the usual route . . . but this time the way was blocked by a mob of sans-culottes so unappeasable that even General Lafayette couldn't disperse them. For more than an hour, they surrounded that carriage, lobbing volleys of spit, every species of Parisian invective-baying for the head of the Austrian bitch and her cuckold. And through it all sat the King and Queen of France, trapped by their own subjects . . . knowing in their heart of hearts they would never again see SaintCloud.

But maybe, during that long hour, they allowed themselves a hope. That one day, not too far distant, their son would breathe that air once more.

A nd once mo re I gaze at this plump bourgeois gentleman with his steel-tipped bluchers and his three waistcoats, strolling down from the Terrasse des Orangers, moving with inerrant straightness, as if a silk train were unfurling behind him.

Is this why you came here? To finish their journey for them? And then Vidocq's voice comes jabbing in.

"Jesus, quit staring at him, Hector!"

The King of France's park boasts a shrub, lately arrived from the Indies. A tangle of branches, fine as hair, powdered with millions of tiny white blossoms. Its positioning near the Fontaine du Gros Bouillon gives it a certain status so that, if you're anywhere in its vicinity, you feel obliged to pay respects. The missionary ladies stop for a bit. Also a gitano in an embroidered blue turban, and in the same crowd: an abbe with a torn cassock; a pair of mariners, somewhat the worse for last night, locking arms round each other to keep themselves erect; and a pride of Russian soldiers, tilting their shakos at the exact angle of defiance they sported when they were occupying Paris three years ago.

Even Monsieur Tepac joins the throng. Through Vidocq's binoculars, I see him fold his hands into his waistcoats and bend ever so slightly forward. A f luttering of eyelid, a quickening of nostril.

One minute, that's all he grants this particular plant. Then, gripping his staff like a scepter, he continues in the same stately fashion toward the Grand Cascade, where even now, the emerald water I remember from childhood is pouring through those gargoyle mouths.

He hasn't said a word to anybody in the crowd, but his leaving somehow loosens the social fabric. The missionaries disperse, and the Russian soldiers make toward the nearest restaurant, and those two sailors unlock arms and go careening northward, in widening parabolas.

"Those sailor boys will . . ."

This is what I'm about to say. Those sailor boys are going to kill someone if they're not careful.

And I look over at Vidocq, and I see, stamped on his face, the same thought-carried to a different conclusion.

"Goury," he says. "It's time to break up this party."

H ow did he know? Curiously enough, it's the thing he was at such pains to correct in me.

Their skin.

Not the sun-cured crust that Vidocq remembered well from his own

brief career at sea but the lymphatic whiteness so exclusive to Paris.

And once that discordance has registered, every pretense of being a bystander vanishes, and Vidocq is calling back to Goury and driving forward, like a baggage wagon breaking free of its harness, powering toward the Grand Cascade. . . .

And already he's too late.

The two sailors have shaken off their drunken fog, and in the same breath, they reach into their pockets and converge on Monsieur Tepac, moving in the straightest possible line with the least expense of energy.

Oh, it's evil.

The staff is knocked from Tepac's hand. The first blade catches him in his left side. A foot-deep thrust that freezes him in place for the second blow, a long slash across the neck.

An instant, that's all it takes, and the sailors have f lung the blades away and peeled off in opposite directions, and Vidocq, his face a furious purple, is barking orders at Goury and sprinting down the chateau terrace, and Goury is heading straight for the woods, and Monsieur Tepac is still, against all possibility, standing.