Marks’s Wares: A sampling of his gallery’s big sales. Andreas Gursky Stateville, sold to private collector, May 2004. Brice Marden Red Rocks (1), sold to private collector, May 2002. Nan Goldin Self-Portrait on Train, Germany, sold to Tate Modern, London, July 1997.

It was pouring in Minneapolis, and at 9 A.M. sharp, Marks and his boyfriend, Jack Bankowsky, set out to tour the circuit of open houses that Minnesota’s biggest art collectors were hosting at the Walker’s behest. These outings serve a dual purpose for Marks: They are a sort of sales trip, in which he gets to play the influential Manhattan gallerist before status-conscious heartland collectors for the sake of drumming up business. But they are also field trips into midwestern domesticity for Marks and Bankowsky, who greet each destination with a heavy dose of irony. Marks hired a Town Car for the occasion, and it deposited the two of them first at the home of Ralph and Peggy Burnet, they of the enormous home-sales empire.

The house, in the suburb of Wayzata, is a series of white geometric shapes stacked on top of one another and relieved by rows of enormous plate-glass windows. “That’s a big, nice house,” Marks said. “I mean, I don’t want to live there, but it’s grand.”

“I’m looking forward to seeing some art and some real estate today,” said Bankowsky, who teaches in the art program at Yale and was formerly the editor-in-chief of Artforum magazine.

Marks and Bankowsky ran between the raindrops from the car into the Burnets’ open garage door, beside the couple’s Maserati and Mercedes sedan. They entered the house through the mudroom.

“Hellooooohhhhh,” a woman’s voice called out. “Hi,” Marks mumbled, most certainly inaudibly to Peggy Burnet, who materialized shortly.

“Oh, hey, you guys,” Burnet said. She was blonde and sporty-looking and appeared far too young to have five grandchildren. She had on a green-and-pink tweed Chanel jacket. “I thought, Who’s coming in through the garage? How gross. But it’s you fellas.”

Marks and Bankowsky said nothing, until Burnet invited them to join the party. “Okay,” Marks said sheepishly, looking at his boyfriend as if the two of them were being dragged to the winner’s circle at a NASCAR rally.

To call Matthew Marks awkward would be a bit like calling Bill Clinton ambitious—and as with Clinton’s primal ambition, Marks’s social diffidence can be both a strength and a weakness. Marks is tall, about six-one, but stoops so self-consciously in public situations that at first he appears to be bowing in a gesture of mock formality. And although he is fit, thanks to constant dieting and time at the gym, he was overweight into his twenties, and that seems to have left him partial to generous, black, smocklike clothes—this goes for both jackets and shirts. Marks has a high hairline and a circle of curly locks behind it that puts one in mind of the paper frills on a crown roast. His only concession to a normal human level of interest in his appearance are his eyeglasses, which are black and perfectly round in an anachronistically modish way, in the manner of Harold Lloyd.

When Marks speaks, his tendency to self-edit is so overwhelming that he often ends up expressing himself in virtual pantomime: rolling his open hands at the wrists and making pain-stricken faces. You’re especially apt to get anguished expressions if you force him to talk about himself, or the role he plays in developing his artists’ careers. “I’m nothing without my artists,” he has said.

Marks and Bankowsky have been together for eleven years and live in a townhouse in the West Village. “When we met, Matthew’s gallery was just taking off, and I hadn’t been in charge at Artforum for very long,” Bankowsky, smartly dressed and more outgoing than Marks, said. “We both figured each other was a person worth knowing. Then, after we’d known each other six months, we moved in together.”

The Burnet house was chockablock with the work of major contemporary artists: Ellsworth Kelly and Gary Hume (both of whom Marks shows), and a bunch of significant pieces by Damien Hirst, including, in the living room, six skeletons in a glass case and a large canvas of multicolored dots arrayed in rows against a white background.

Upstairs, outside the master bedroom suite, a middle-aged couple paused to admire another Hirst sculpture: thousands of bronze, hand-painted pills laid out single-file on a mirrored metal grid.

“Now, when you’re mounting it, does he specify where the pills go or not?” a woman asked Ralph Burnet, a small man with strawlike gray hair.

“Yes, he sends them in boxes, and they’re all numbered,” he said.

Downstairs in a hallway, there was a knot of people staring at an installation by Maurizio Cattelan: two tiny electronic reproductions of office-building elevator doors built into the wall at floor level. They were constantly lighting up and opening and shutting.

In the kitchen, Peggy Burnet was on the telephone. “Good morning, Ellsworth,” she said. “Yes, they are all here. I’m just delighted. Now, when are you coming by?”

She looked at Marks and mouthed the words Ellsworth . . . Kelly. The visitors filed out of the Burnets’ house. Most headed for the bus that had been chartered by the friends of the museum; Marks and Bankowsky got into their Town Car.

A large Richard Serra sculpture, consisting of nine black Corten-steel walls arranged in neat order, came into view in the Burnets’ backyard. It was a reminder of why the Burnets were important to Marks, who sold it to them four years ago. His deferential and withdrawn demeanor has pointed up his awareness that he’s been in the home of potential big art buyers, but his typically soft-sell manner has kept him from overplaying his role as a sales broker.