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“Doctor’s in the house!” bellows Robert Wiedmaier, coming down from his perch in the kitchen at Marcel’s. The chef-proprietor claps his hands like a coach exiting a huddle. The front-of-the-house staffers hardly need the encouragement—they know the drill. A tense alertness comes upon them as the Mercedes pulls up to the door.

In walks William Hall, resplendent in topcoat and fedora. Two staffers descend on him, one to take his hat, the other to help him with his scarf and coat.

“Dr. Hall, good to see you again.” This is Adnane Kebaier, the restaurant’s maitre d’, who leads Hall by the elbow toward the bar, where a group of real-estate agents is celebrating. Packages and purses have been stacked atop the seats. The doctor waits.

“Ladies?” Kebaier directs their attention to the seat at the end of the bar—specifically, to the gold plaque affixed to its back: “Reserved for Dr. William S. Hall.” The doctor’s place has already been set; to the right of the plate are two glasses, a flute for his Veuve Clicquot and a goblet for his Neyer’s chardonnay.

Hall takes his seat, reaches into the breast pocket of his jacket (Brooks Brothers, pinstriped) and removes a slim silver case of cigarettes and his filter. The bartender produces a light. The ladies are buzzing. Who is this dashing older man who commands such royal treatment?

Marcel’s has long been a haven for local celebrities. But Hall is not one of them. Not even close. He’s an academic, the dean of psychology at the University of Maryland at College Park, and unless you’re acquainted with the finer points of cognitive neuroscience, you’ve probably never heard of him.

But the 71-year-old Hall is a bigger VIP at Marcel’s than Rummy or Condi or the dozens of personages—“recidivists,” cracks manager Tom Burke—who count themselves as regulars at the West End restaurant. More famous though some of these regulars are, none are more devoted than Hall.

Six years ago, Hall was strolling along Pennsylvania Avenue one day when he saw construction going on inside the shuttered Provence. Chef Wiedmaier was on the sidewalk, supervising workers. “Come on by,” he urged. “I’m open on Monday.”

Hall came on by for that soft opening, and he has come on by for dinner nearly every night since. According to Wiedmaier’s estimates, he spent between $50,000 and $60,000 at the restaurant last year. But what looks to the outsider to be a costly indulgence, Hall contends, is actually a justifiable expense “when you consider the cost of groceries at a place like Dean & DeLuca and the time it takes to cook all of it, and then all the food you inevitably have to throw away.”

He is more comfortable, and more convincing, talking about the profound role the restaurant plays in his life, the sense of structure it provides. “I’m in science; predictability is important to me….My seat is here. This is where I come every night. Even if I’m eating something different, I’m still eating it here. That’s just my personality. I don’t like lots of change.”

The “idea of a place I call my own,” as he puts it, has long held an allure for Hall. As an undergraduate at the University of Chicago in the ’50s, he was a regular at the Hobby House, a joint at the other extreme of the restaurant continuum. He ate the same thing every single day: “Hamburger with chili, Coke, and fries. Ninety-nine cents.” It was the attraction of “stability,” he says, more than the cheap eats, that had him coming back day after day.

Even at Marcel’s, the food, sumptuous though it is, is only part of the reason he keeps returning. There is also his “fascination…with the total organism, the way all the elements in a place like this come together”—a “holistic thing” he sums up in a single word: “ambiance.” He pronounces it with a flourish: “ahm-bee-AHHHnce.”

Having spent a lifetime looking at systems, Hall has come to believe that Marcel’s would make an interesting laboratory for a study in organizational psychology. Of course, any such study would have to include the professor himself, who has become as integral to the functioning of the organism as any runner or server or manager. Just how much Hall has insinuated himself into the whole becomes manifest when Ramon Narvaez, the sommelier, drops by the bar to make sure tonight’s chardonnay is to the doctor’s satisfaction.

Narvaez taps at his pocket square. Its three-point arrangement mirrors that of the doctor’s own. “Dr. Hall said, ‘You would look so much better with a handkerchief.’ He took me to Brooks Brothers. Everybody knows him there.”

Narvaez points to his shoes. Gucci loafers, the same as Hall’s. “We all wear them now.” He gestures toward the host stand. “Adnane, you notice, is a Gucci shoe fan.”

A custom-made basket of crostini is deposited on the bar—Hall favors two kinds, one plain, the other slathered with pesto—and Narvaez produces a new wine for the doctor to sample: an ’03 sauvignon blanc from Napa. He presents the bottle for inspection: It’s from Hall vineyards.

The regular chuckles softly at the in-joke, another of the “touches” by which Marcel’s distinguishes itself. “You see what I mean? Ambiance.”

Narvaez beams. “Are you ready for a little dinner, Doctor?” he asks. “Would you like the chef to surprise you? You haven’t had the boudin blanc in a while.”

The doctor strokes his neck, considering the possibility. “I think maybe,” he says, “the chef and I should chat.”

Wiedmaier materializes a minute later, draping his arm across Hall’s shoulders as they decide upon a menu.

The chef and the doctor are bound by more than just their professional interaction. Psychology is the doctor’s profession, the restaurant his continuing obsession; in Wiedmaier’s case, it’s the converse. He’s fascinated by what he calls the “psychology of the business,” the “delicate dance” of making sure a loyal customer is also a happy customer. Every night he reminds his staff: “You cannot take our regulars for granted. One thing goes wrong, and it doesn’t matter what it is or how long they’ve been eating here—they can become monsters, your worst enemy.” One couple, longtime customers, were dismayed one night to find the restaurant was out of their favorite vodka. They didn’t return for five months.

“Service at this caliber,” Wiedmaier insists, “is more important than food. I swear by it.”

The chef expresses his gratitude for Hall’s patronage in a variety of ways. That nameplate is attached to a specially installed swivel stool—“the good doctor,” he notes, “likes to look around.” Twice a year, he invites Hall to host his colleagues to a dinner party at the restaurant, free of charge. He hooks him up with wholesale suppliers for caviar and champagne. He has him over for Thanksgiving every year. And, although Hall lives just a few blocks away from Marcel’s, the chef keeps a Mercedes at the ready, awaiting the doctor’s call for a ride.

The salad arrives. Hall eats slowly, methodically, sipping from his chardonnay between bites. After a leisurely, well-timed interval—not so soon after the first course as to seem rushed but not so long after that Hall becomes impatient—along comes his appetizer-size portion of Dover sole.

“You are happy with the sole, Doctor?” Narvaez surfaces to ask.

“Delicious. As always.”

Wiedmaier marvels, privately, that Hall knows his cooking almost as well as he does. After all, the chef says, “He eats it more than I do.” He wonders sometimes how a person can taste the same dishes, the same style, night after night and not get bored.

But more than variety, Hall says, what he seeks is a certain contentment, the pleasurable repetition of a gentle, civilized experience. Occasionally, he says, he visits other restaurants in town. In one way or another, they all come up short: One high-end establishment has food that is “too gooey. I don’t like gooey.” Another is “fine but just too far away. I don’t like going downtown. I don’t like going to a neighborhood like that.” Above all, he cannot tolerate “fluff.”

“There is no fluff here. They take themselves seriously, and they take you seriously.”

Should he see any sign of slippage, Hall does not hesitate to point it out. This does not happen often, Wiedmaier notes—the doctor is “not a big complainer, like some.” But when he does voice his displeasure, it carries added weight, because the chef and his staff know he speaks from authority. Not long ago, Hall warned the chef of a propensity for oversalting in the chestnut soup. Tonight, it is Narvaez he chides, albeit gently, like a kindly benefactor. The onetime runner he has watched move up through the ranks to become sommelier pops the cork on a bottle of garnacha and tells a nearby customer of his great love of Spanish wines. The doctor interrupts this little valentine with a bit of dramatic throat-clearing.

Narvaez looks up, chastened. “Thank you, Doctor.”

Hall later explains his action: “He was talking about himself too much. He’s got to watch himself.”

The night passes in languorous splendor. The real-estate agents have long since left. Other customers in the dining room come and go. The doctor agrees to a cup of coffee (no dessert tonight) and allows himself a final cigarette before taking his leave for this evening.

The front of the house is prepared, as responsive to his departure as it was to his arrival. No sooner has the doctor stepped down from his stool than Narvaez appears at the host stand with fedora and coat and scarf. Hall smiles approvingly. He glances outside, noting the Mercedes that is idling at the curb. Am-bi-ance. He glides through the front door toward the waiting car.

“Stop by tomorrow,” Narvaez calls out cheerily. —Todd Kliman

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