Susan Ford was ironing her husband's shirts, watching a soap opera when the bulletin broke in President Reagan had been shot.

As the videotape of the incident ran, a chill went down her spine. Then another videotape ran, the one of her father, former president Gerald Ford, being shot at by would-be assassin Sara Jane Moore.

"I thought, 'My God, who do I have to go through this again?'"

She raced to the phone and called her husband, Charles Vance, ex-Secret Service man and her father's former bodyguard who now runs a private security firm in Fairfax, Va. Vance left his office, climbed behind the wheel of his charcoal gray Buick Riviera and drove to the couple's home in a nearby development.

Fear had brought them together one more time.

"We both understand each other's position," she says, acknowledging their special relationship of former protector and protectee. She is his "Princess." He is her "Superman." Yes, she says, she is learning about fear from her man of steel who still cases every crowd, every room, always looking over his shoulder, always riding shotgun.

"I know what his [Reagan's] kids are going through. Your first emotional reaction is, 'My God, my father's been shot at,' not the president of the United States," she says.

Her husband knew the other side: what the Secret Service agents were going through.

Their unlisted phone rang off the hook that day: reporters wanting quotes, former Secret Service buddies with information, ABC'c "Nightline" wanting Chuck Vance for Monday night, "Good Morning America" begging him to do the show.

"My initial response was not to say anything," says Vance. But then he changed his mind. He knew those Secret Service men had acted quickly, even heroically. He studied the videotape and timed their response. It took them 13 seconds, he says, 13 seconds to get the president away.

He knew Tim McCarthy had saved Reagan's life. He watched McCarthy react to the first gunshot, then stretch his body straight up, making himself a bigger target, taking the bullets the way they had practiced so many times. He watched hid old friend Jerry Parr dive on top of the president.

"Jeeezus Christ," he says, gritting his teeth.

When the limousine arrived to whisk him to the studio, Vance knew he could also talk about the stress of being a Secret Service agant, the anxiety, the often unbearable tension -- like a boxer always training for that big match. And besides, bad news is good news for security firms.

Business, by the way, is booming.

"Now they no longer introduce me as 'Chuck Vance, Susan Ford's husband,'" he grins, basking in the spotlight once reserved for his presidential princess.

Now he is Chuck Vance, head of MVM International Security, Inc. Vance is a darkly handsome, well-built man of 39 with a trim mustache, cool Mediterranean blue eyes and a hot temper. He wears natty suits, silk ties and a gold chain bracelet. He is a pistol-packing, high-strung soldier of misfortune who is banking on the current increase in terrorism and tutoring his young bride -- once No. 3 on the SLA's "hit list" -- in the art of paranoia.

"I'm getting better," she says. "I'm more fearful than I was."

She is a cool champagne blond with chin-length hair, large tortoise shell glasses, turquoise eyes and a Creamsicle complexion. She is athletic-looking, tall and large-boned. Preppy. Attractive. She looks older than 23, bakes her own bread, attends aerobic dancing classes twice a week, "lives" on the Scarsdale Diet and mostly stays home with their 8-month-old daughter Tyne Mary.

"All my life I've had one dream," she says, bouncing the baby on her lap in the living room of their four-bedroom home. "To be a wife and a mother."

She is no longer Susan Ford, flirtatious and flighty daughter of a president, she says. She has grown up. Matured. Her old friends say she's gotten straight, boring even. She is Susan Vance. She is secure.

"Maybe it's because my father traveled a lot when I was younger," she says. "We didn't really have a tight, close-knit family. Maybe I was jealous of other people's families."

So -- after a rocky romance and against her parents' advice -- she married her father's bodyguard, her protector's protector.

"Chuck has a lot of the same qualities I admire in my father," she says. "He opens car doors for me. Things like that."

He has, she says, given her confidence.

They met in 1977. He was a 14-year veteran of the Secret Service, divorced father of two adopted children, native of Chicago, former cop and bodyguard for Hubert Humphrey, Spiro Agnew and Mo Udall and newly assigned supervisor of her father's Secret Service detail in Palm Springs. She was the golden girl, the free-lance photographer, the first daughter who had her prom in the White House and her picture in People.

The first meeting.

"She was hanging around the command post in a pair of cutoffs. Her hair wasn't done or anything and she was about 30 pounds overweight. Nobody introduced us, so I walked up and said, 'Hi Susan, I'm Chuck Vance.' She gave me a look like I had dog poo-poo on my shirt."

"I thought, who the hell does she think she is? I thought she was a snob."

Hate at first sight?

"Well, I wouldn't call it hate," Susan Vance says now. "More like dislike."

Susan had graduated from Holton-Arms, a private girls' school in Washington, attended Mt. Vernon College for a while, then moved West. At the time, she was studying photography at the University of Kansas.

"Nobody would talk to me," she says. "I never had one date the whole six months I lived in Topeka."

Depressed and bored, she went to Vail, Colo., with her parents and attended a party one night. Vance was there. They talked. They drank. They made a date for dinner.

"No, it was drinks," she corrects her husband. She remembers because when she walked into the restaurant, he had already ordered her favorite cocktail: Kahlua and cream. "I thought, this man is something," she recalls.

They began dating secretly. She left her code name when she telephoned him: "Just say "Trouble' called."

By her account, Chuck Vance put the former president's daughter through "hell." He had recently divorced, he says, and was spreading his wings, playing the field. "I told her from the beginning I didn't want to get serious," he says. "I said it would never work."

They broke up a dozen times. When he asked for the key to his apartment back, Susan Vance says she went "berserk. I jumped up on his balcony, screaming."

She dated other men to make him jealous. It worked.

"His feeling was it was all right for HIM, but not for ME," she says indignantly.

"Now, honey . . . " Vance mumbles.

"It's true," she says.

She had quit school and moved to Palm Springs. She got a few photography jobs, including shooting the stills for "Jaws II." But she was anxious to settle down.

"I knew I had to make a decision," Vance says. "Either we had to come out in the open, no more sneaking around, or we had to end it."

She told her parents they were dating. "They had some reservations about the age difference," Vance says. "And the fact that I was divorced was a problem. You know, there was a feeling of nobody was good enough for Susan. I figured they'd rather have her marry Prince Charles.

"He's gone now," she says.

"Maybe he gave up when you got married."

When he proposed, she burst into tears. They were engaged in October 1978, and married the following February.

"If I had to do it all over again I'd elope," she says. "Chuck and I had out worst fights the week before we were married."

Now, she says, the marriage is "very stable. I have no intention of it failing. If anyone gives up it would be Chuck."

Her mother, Betty Ford, once made headlines by saying she would not be surprised if her teen-age daughter had an affair. Would Susan Vance be surprised if her husband had an affair?Chuck laughs.

"Yes," she answers. "In fact, that's the only thing I would divorce him for."

She says she had to "talk Chuck into having a baby. When I called lhim and told him I was pregnant, he wasn't extremely ecstatic."

She decided to have a child, she says, becasue she was "semi-bored with work" and also because of Chuck's age. "That was a factor," she says.

Vance left the Secret Service shortly after his marriage and opened his security office in Anaheim, Calif., with two other ex-Secret Service men.

"I went through withdrawl at first," he says. "It gets in your blood. Protecting a president is a hard act to follow."

Being in the Secret Service, he says, is "tremendously stressful. it burns people out. Every year, they have a physical examination and monitor their vital signs. Every year, those signs begin to deteriorate: high blood pressure, things like that. One doctor who did a study compared it to battle fatigue."

The stress causes family problems, also. "There's a high rate of divorce," he says. Indeed, Chuck Vance says it still takes him an hour or so to unwind after a day at work. "I find it hard to relax," he says, jumping up for the third time in three minutes to answer the phone.

He feels the rise in violence and terrorism is linked to the economy, that there is no longer the light at the end of the tunnel for many people. "They're turning to crime," he says.

Bernard Welch, alleged master theif and accused slayer of Dr. Michael Halberstam, is suspectewd of burglarizing two homes in the Vance's development. Already, a dozen or so neighbors have hired Vance's company to install thousand-dollar alarm systems in their homes.

Vance opened the Fairfax office last September and employs about 26 fulltime agents who are hired out as bodyguards and are experts in security devices. Vance himself recently spent two weeks in Mexico guarding an unnamed celebrity.

"The climate of the world is what's making us prosper," he says. It's too bad, but it's a fact of life."

The Vances own land near Vail, Colo., where they are planning to move in five years or so. Out there, the Princess and her Superman hope to "live happily ever after."