Best-selling suspense novelist Mary Higgins Clark keeps more people awake than bumps in the night.

Such a nice lady to think those terrible thoughts!

Her manner so sweet, as if dipped in sugar. Her conversation, confidential. Her smile, sympathetic. Her clothes, exquisite. And her eye makeup, expert.

Aha! Those eyes! The depths of her deep green-blue chameleon eyes are bottomless pools, brimful of tears of terror. She has that chasm-deep knowledge of primeval fears one learns as a convent school graduate, a mother of five, a widow of many years and a friend to all: fear of falling, fear of dying, fear of losing love. Her mind is beset by awful anxieties about perils that can befall the innocent: the old wives' tales of wicked lovers, butcherly gynecologists, endangered children, lonely roads, empty houses.

What is it like to live with a mind so hagridden?

"I love it," she says, looking proud, happy, calm and content in Washington to talk about her new fright tale, "Weep No More, My Lady" (Simon & Schuster), and also to be feted by those who served as technical advisers (Frances Humphrey Howard, for one) on the book before, her Washington novel "Stillwatch."

"Weep," a Literary Guild main selection and No. 4 on the best-seller list, is the sixth of her literary disturbers of the peace. Four were filmed for TV or the theater, and several more are in the works for TV. Her first five books (also Simon & Schuster) are now Dell paperbacks and constantly on the presses.

Her genre is sometimes called "If I had but known." A subgenre could be: "It's all my fault. If only I hadn't ..."

From "Weep":

Elizabeth began to shiver uncontrollably at the image she could not banish from her mind: Leila's beautiful body, wrapped in the white satin pajamas, her long red hair cascading behind her, plummeting forty stories to the concrete courtyard ... If I had stayed with her, Elizabeth thought, it never would have happened ...

But don't misunderstand: Clark's heroines don't bring the disasters on themselves. That's what makes their tragedies so fearsome.

"I write about nice people whose lives are invaded," she says. "What scares you is the 'if only' -- the thought that whether you live may depend on the moment when you decide to take a bus or a train."

Malice, murder, madness and mayhem have always menaced her waking hours.

"When I was very small and went to pajama parties, I would tell stories that began, 'Someone -- or something -- is standing behind the curtain, watching ... And his eyes will fall on one of us. I wonder which one?'

"I write suspense because it's what I like to read, have always read," she says.

She has been a writer since she was 7 and her mother gave her a five-year diary with a key.

"Nothing much happened today," she wrote, setting no pattern for her later work. She still keeps diaries. "They're a wonderful help to my novels -- I can read them and know what I was like at all ages." She's kept them all. "They're locked in a trunk, hidden. Even the children can't read them until I'm gone." Unlike her mad gynecologist in "The Cradle Will Fall," she does not keep her records behind a bookcase that swings out to reveal a hidey-hole.

Clark has known about writing for money as well as love since high school in the Villa Maria Academy in the Bronx. "I sold poems at a dime each for those who needed them in class and had forgotten to write their own," she says.

And by the sweat of her brow and the cold sweat on her readers', she makes a good living now -- supporting houses in New Jersey and Massachusetts as well as a New York apartment on Central Park South. She's ranked by industry insiders as one of the most financially successful American woman authors -- with more than 10 million copies in print just in this country.

Once upon a time, it wasn't so.

Her father died when she was a child, leaving her mother with a ledger of uncollectible debts from his Irish pub in the Bronx.

"He died of anxiety -- a disease of the Depression," she says. "Those were awful years. Well-educated people who'd worked hard couldn't find jobs. They'd come to the door so apologetically, saying, 'Excuse me for bothering you, but could you spare anything to eat?' My mother used to keep a card table set in the foyer for them."

A scholarship student at Villa Maria, Clark worked after school as a baby sitter and as a telephone switchboard operator in a small hotel.

"The head operator warned me: 'You mustn't listen in on Maggie Ryan's calls.' She was a lady of the evening and had lots of calls from men," Clark says. That's one experience she hasn't used yet in her novels. "It's not as easy now to listen from a switchboard without anyone knowing," she explains.

Clark's stories of her life -- she makes everything into an anecdote -- sound as though they came out of her books. And she tells them dramatically, explaining, "I won a medal as the best actress in the Bronx."

After graduating from high school, she spent three years as a secretary in Remington Rand advertising. She was enticed into a job as an airline hostess, "then a lot like being a starlet," she says, "by seven words that changed my life." A stewardess friend, resplendent in her Pan Am uniform, met her in a cocktail lounge, sighing, "God, it was beastly hot in Calcutta." Oh, the glamor! The world weariness! The adventure!

For her farewell dinner, she had her first date (though she'd known him forever) with Warren Clark. That night, they became engaged when he started making out the list of who would be invited to their wedding. But he agreed to her Wanderjahr in flight, which lasted a year.

After they married, she signed up for a writing course at New York University, writing her stories on her kitchen table, a` la "Murder, She Wrote." "It's a great place to write," she says.

Even so, it took her six years and 40 rejection slips before she sold her first short story for $100 in 1956.

"My first writing teacher told me: 'Write about what you know,' " she says. So she wrote about her experience as a stewardess, among other things, in several articles and short stories (and eventually in "The Cradle Will Fall"). Just when she was selling well, the bottom fell out of the magazine short story market.

"When my husband died in 1964, after three heart attacks in five years, I had five children, from 13 years old down to 5, and enough to live on for two years -- Warren wasn't insurable nor eligible for his company's pension plan. That first year after he died, the children had 13 sporting accidents."

So Clark began to write radio scripts, first at home, then in an office. She also began to write books.

"I would get up at 5 a.m. and write until the children got up at 7 a.m. I still am at my best in the morning. I begin with a cup of coffee at my computer at 7:30 a.m."

Her first book was "Aspire to Heaven," about George Washington. "That was great because it showed I could write a book." And then she wrote "Where Are the Children?" -- first turned down as too horrifying to women readers. Published by Simon & Schuster in 1975, the book was an immediate best seller. When the paperback, now in its 20th reprint, was sold to Dell for $100,000, she didn't have to worry about the children's tuition at Dartmouth, Mount Holyoke and the Immaculate Heart Academy.

So she signed up herself for three-nights-a-week classes at Fordham University, from which she graduated summa cum laude in 1979. In the meantime she wrote "A Stranger Is Watching," published in 1977 ("My first big advance -- $500,000. The paperback rights went for a million dollars. That's when I went out and bought a Cadillac and a mink, what every red-blooded Bronx girl would do").

"The Cradle Will Fall" was published in 1980, followed by "A Cry in the Night" in 1982 and "Stillwatch" in 1984. The settings and characters became less domestic and more sophisticated as Clark's own life changed. "Stillwatch," for example, is about a television producer in love with a senator who lives in a house on N Street in Georgetown -- carefully researched not to be a real number, of course.

Even so, all her books might be said to be about losses. Her heroine is likely to be a woman in her late twenties or early thirties who has already suffered a loss. Husbands, children, parents, siblings -- Clark heroines lose them like earrings. Men suffer, too.

From "Weep":

"Teddy is the name of a two-year-old boy. I'll describe him for you. He was what my grandmother used to call a towhead ... very, very blond. He was a tough little guy who walked at nine months and spoke sentences at fifteen months. He was my son. His mother was a very sweet young woman who unfortunately could not get used to the idea she had married a very rich man ... One rainy night she was driving back from grocery shopping and -- we think -- a goddamn can of tomato soup rolled out of the bag and under her foot. And so she couldn't stop at the stop sign, and a trailer truck plowed into that god-damn piece of tin she called a car. And she and that little boy, Teddy, died.

But you can't accuse Clark of making her heroes and heroines suffer worse than she has.

Her father's death came when she was 11, her husband's when she was 36. As she was trying to revive her husband with mouth-to-mouth resuscitation after his fatal heart attack, her mother-in-law collapsed and died. Her 18-year-old brother had been killed in World War II. Another brother died at 42 in an accident. Her mother, who had helped Clark make time for writing, died before Clark's first book was published. And now, a son-in-law, husband of her youngest daughter, Patty, is fighting leukemia.

"One thing about having someone seriously ill in the family," Clark says. "Nothing else matters. You don't worry about trivialities such as the washing machine breaking down.

"I have lost people, but I've been blessed with grandchildren and friends and a career."

She mines her life for her books. They're full of children. The character names come from her Christmas card list. The settings, too, are real -- she visited Main Chance in Arizona, La Costa in California, and Brener Park in Baden-Baden, West Germany, for the new book. She had a California friend read the book to review the geography and a doctor friend to check the lethal dosages. But she never gives credit to her experts until the next book. "That's so if the book is panned, they don't go down with the Titanic," Clark explains.

Her first book, etched in the nightmares of every mother who ever read it, had a scene right out of Clark's life. Patty was 3 "when we moved to the lake. One day I couldn't find her and I screamed, 'Go to the lake.' I found her later, asleep on the couch." Her heroine is not as lucky. Her children aren't in the lake -- yet -- they've been kidnapped, though everybody believes the heroine has murdered them.

Her heroines are talented, pretty, virtuous -- and often based on her own daughters. But in the books, they're a shade too trusting, a bit too sympathetic, a lot too vulnerable.

In the course of the novels, the heroines grow up, change, learn something about anatomy -- principally the location of their backbones and her minds. At the end, they kiss the desirable but disguised-as-toad men who have always loved them. The toad-heroes turn into princes, complete with more money than a TV preacher. And then, the riveted reader can turn out the light and try to get to sleep, with visions of lethal needles dancing in their heads. You might call them fairy tales for our times.

Clark lives alone and writes and rewrites most of her books (almost all come out at 425 typewritten pages, she says) in her New Jersey house in Washington Township. She has two computers, a copier and many files. She says she rewrote "Weep" four times over two years.

"I'm not as prolific as Stephen King. But I always feel guilty if I'm not working," she says.

And so there's more to come. Currently she's working on a book about a teen-age daughter who disappears, titled "While My Pretty One Sleeps"; a television version of her Woman's Day novella, "Terror Stalks the Class Room"; and a mini-series on "The Anastasia Syndrome." She's also negotiating a mini-series of "Weep."

Clark knows how to extract every second out of a minute. "All my books are in a very tight time frame. The clock running down adds to the suspense."

From "Weep":

He had known for months that it would be necessary to kill Elizabeth. He had lived with the ever-present knowledge of the danger that she represented...It was midnight in New York. Sweet dreams, Elizabeth, he thought.

Your time is running out.

She's certainly extracted more time than was there for herself.

"If you'll notice, in Who's Who, I've been getting younger all the time," she says. "But I've finally decided to accept the Oriental view of the glories of age and admit I'll be 60 at Christmas. I'm looking forward to the next decade as my most exciting years."