When I'd call her Mariel, everyone would turn around, so I'd just say, 'Hi, Sam,' " explains Stephen Crisman of the young Hemingway he ended up marrying in December 1984. For her part, Mariel found she liked the anonymity of being called Sam. "It gives me a real sense of being normal," she says. It also provided them, once romance had flowered and wedding bells had rung, with the name for their first joint project, a restaurant on Manhattan's Upper East Side.

Sam's Cafe came about when the newlyweds started making plans for the future. High up on their list was the hope to someday start a restaurant. That wasn't surprising, considering that Stephen, now 36, has been in the restaurant business since he was 20. His career includes being a co-founder of London's successful Hard Rock Cafe, and until March 1985 the manager of Hard Rock's Manhattan incarnation. In fact it was at the latter that the two met. "I hadn't seen any of her movies," Stephen admits. "At first I didn't know who she was." For Mariel, now 24, it was true love from the moment she was introduced. Says Hemingway, who was raised in Ketchum, Idaho: "He looked like he was from my part of the world, although it turns out he's really from Virginia."

The site they picked for Sam's Cafe is far enough uptown to need a neighborhood clientele to succeed. After the $750,000 renovation of a defunct Mexican restaurant, Sam's Cafe opened in late January. An early rush of celeb well-wishers, including Robert De Niro, Kevin Bacon, Walter Cronkite, Mort Zuckerman and Ahmad Rashad, were enthusiastic. "I'm a pasta fanatic," says Rashad, "and they've got the best pasta in town. Sam's is my spot."

Mariel insists that Sam's Cafe must be a place where people are not intimidated and feel they'll be treated well no matter who they are. "On a very superficial level," she explains, "I can go on David Letterman and get customers, but I can't keep them in the restaurant just on the public image."

To attract diners, Mariel has designed Sam's spare but homey decor in what could best be called Basic Bovine. There are pictures of cows everywhere, behind the bar, on the menus, even an enlarged bull's-eye print done by Milan Tiff, a triple jumper Mariel met while she was filming 1982's Personal Best. For Hemingway, cows are an amusement. "Maybe because they have a calming effect on me," she says, "or maybe it's because I'm from Idaho. I hope nobody hates them too much."

The state also influences the menu. Although Mariel's diet is predominantly vegetarian, she points out, "I know a lot about food. My mother is a Cordon Bleu-trained cook, my sister Muffet is a great pastry chef, and my father grew up in Paris, so I was raised around really great food—I've never eaten at McDonald's. Plus I was always reading about nutrition." At Sam's, she says, "We didn't want any of this nouvelle cuisine where the plate has more decoration than food." The menu, instead, is "good simple food—pasta, fish, steak, grilled chicken—and the chickens are organic." (The price: about $55 for two, without wine.)

Mariel and Stephen take their meals nightly at the corner table in Sam's back room. "I don't want to be up front," Hemingway has explained. And, indeed, Crisman is the impresario, constantly making the rounds and chatting with customers. "Stephen makes it work," Mariel says proudly. "It has to do with his personality." Being a night owl doesn't hurt either. Mariel, a day person, leaves the cafe every night by 10, Stephen closes up sometime past midnight.

Hemingway sees Sam's as "a diversion" and has high hopes that her screen career will soon get rolling. After starring roles in Woody Allen's Manhattan (which got her an Oscar nomination) and in Personal Best, followed by the part as slain Playmate Dorothy Stratten in Star 80, she would like "some Meryl Streep kinds of roles." Her dream, she says, would be to play Zelda Fitzgerald, with Sidney Lumet directing. When she does start making movies again, she says she'll fly in and out to help with Sam's. "That's the way it's supposed to be when you're starting out," she says. "You gotta work hard."