When her bedside telephone rings at 4 a.m., Mary Prinze knows that it's no emergency. Without bothering to pick up, she kisses her husband goodbye and groggily grabs the spare dress she keeps folded at the edge of the bed. An hour later she has sped the family car from rural Tappan, N.Y. to downtown Manhattan and arrived at her switchboard just in time to place her first wake-up call: "Good morning, Mr. Pacino, it's 5 a.m."

Ever since she took down her first message for Hermione Gingold in 1956, Prinze has been on constant call to the stars. Over 400 phone numbers—most of them unlisted—light up the switchboard at Prinze's Belles Celebrity Answering Service. Woody Allen subscribes, as do Candice Bergen, Robert Redford, Tennessee Williams, Brooke Shields, and James Taylor and Carly Simon. Admittance to Belles is by recommendation only. "I don't want people who are struggling," says Prinze, 56, candidly. "I knew I'd made it," confessed Broadway lyricist Fred (Cabaret) Ebb, "when I was finally accepted by Belles."

How has Prinze turned her answering service into an exclusive social club? "We're involved in the lives of our clients," she explains in a warm, motherly voice. For the reasonable fee of $70 to $100 a month, the Belles operators will not only jot messages but also feed fish, accept dry cleaning deliveries and assure Pacino's grandmother that her hard-to-reach grandson is at the peak of health. More recently, during the gasoline crunch, when it took Woody Allen's chauffeur eight hours to get gas, Belles kept the boss posted on the car's position in line. "We get as close to our clients as you can possibly get without ever getting intimate," says Prinze.

Not that Prinze lets her 22 operators take any celebrity static. When Richard Dreyfuss wanted Belles to screen every incoming call after he won his Oscar, Prinze disconnected. "We don't have time to be anyone's personal secretary," she huffs. And after Burt Reynolds accused Belles of giving out his phone number to strangers, Prinze assured him that, if she were going to divulge unlisted numbers, she had more important ones than his.

Mary grew up making the right connections. Born in chic Grosse Pointe, Mich., she grew up in Hampton, Va., where her father—an executive with a pleasure boat company—earned the nickname "Wild Bill" Horn for his stunts, which included winning speedboat racing's triple crown. Mary contracted polio at the age of 4. The disease has left her with a severe limp, but it never crimped her spunk. "The doctors told my parents I would never walk," she remembers. "I told them I would, and I did."

Mary didn't aspire to be Ma Belles. But when her husband, nightclub pianist Bob Prinze, started playing New York clubs, she went looking for a nighttime job and plugged into an answering service in 1954. The pay was only 90¢ an hour, but her constant personal attention earned some influential feedback. Pretty soon she was babysitting on the side for Imogene Coca's poodle and going on Scotch-buying errands for Noel Coward. Adolph Green was so enamored of her that he wrote a Broadway musical about an answering service—Bells Are Ringing—and had its star, Judy Holliday, take her switchboard training from Prinze. "I offered her a job," laughs Prinze approvingly.

By the time Bells opened on Broadway in 1956, Prinze was founding her own Belles service in a cramped East Side studio, using hand-operated sets. There were 18 clients and Prinze worked round the clock. "My husband understood," she says. "I had promised my clients 24-hour service."

Today, with her client list rivaling that of the William Morris Agency, Prinze commands six switchboards and five wastebaskets overflowing with cryptic messages. And the lines keep buzzing. Paul Newman calling Robert Redford. Louise Lasser trying to reach her ex, Woody Allen. Groupies calling the boys from Kiss. At 5:30 p.m. Shirley Mac-Laine calls for her messages. Elton John, she is told, has phoned her. Bella Abzug has too. And at 5:10 yesterday her brother called. Deadpans the operator: "He said you'd know his name."