In the spring of 1955, Grace Kelly was in the South of France, attending the Cannes Film Festival and renewing an old affair with the actor Jean-Pierre Aumont. At lunch with him one afternoon, she mentioned her plan to skip a photo shoot the next day with the Prince of Monaco. It conflicted with her appointment to have her hair done. Aumont was aghast. "Grace," he insisted, "you can't possibly do that! He's a reigning prince."

There wasn't much she couldn't do that year. She was 25, an Oscar-winning actress and a world-renowned beauty. In a short time she had gone from being a Philadelphia debutante to a film star. Alfred Hitchcock had saluted her enchantments that year in To Catch a Thief, and during her long onscreen kiss with Cary Grant, fireworks break out behind them. To sum up the world's opinion of Grace Kelly, nothing short of fireworks would do.

Prince Rainier of Monaco headed the House of Grimaldi, Europe's longest-ruling princely family (established 1297). Though his domain was just 370 acres—smaller than the back lot at Kelly's studio, MGM—it had space enough for his 200-room pink palace and his private zoo. And room as well for the lightly faded Monte-Carlo Casino, which still pumped out sufficient revenue so that none of his 20,000 subjects paid any personal income tax. But under the terms of an old treaty, if Rainier died without an heir, they would all become citizens and taxpayers of France. After a lengthy live-in affair with the French actress Giséle Pascal, Rainier, at 31, was searching for a suitable bride.

Clearly, looks were a priority. En route once to the U.S., he described to reporters his ideal woman: "I see her with long hair floating in the wind, the color of autumn leaves. Her eyes are blue or violet, with flecks of gold." Despite her initial indifference, golden-haired, blue-eyed Kelly's first meeting with Rainier went well. "I think he's very charming," she told Aumont. After returning to the States, she and the Prince began a correspondence that was avidly pushed along by Father Francis Tucker, the American priest who was Rainier's closest aide and chief talent scout for eligible Catholic girls.

Kelly had already been through Clark Gable, Ray Milland and William Holden, as well as the Shah of Iran and the fashion designer Oleg Cassini, whom she had come close to marrying. Her taste horrified her father, Jack, an Irish-American bricklayer turned millionaire builder. Her younger brother once complained, "I don't generally approve of these oddballs. I wish she would go out with the more athletic type."

But by the time they met, it may have required nothing less than a prince to equal Kelly's celebrity. "I don't want to be married to someone who feels belittled by my success," she once said. "I couldn't bear walking into a restaurant and hearing the maitre d' refer to my husband as Mr. Kelly." From his side of the Atlantic, Rainier saw in Kelly a woman who might bring not only heirs, but a touch of glamor to revive his entire domain.

"Their relationship was both rational and passionate," says Rita Gam, a Kelly bridesmaid who remained one of her closest friends. "I love his eyes," Kelly gushed. "I could look into them for hours." When Rainier gave her an immense diamond engagement ring, she flaunted it on camera in her last Hollywood film, High Society. Their wedding week in April 1956 brought them even closer. In the words of one of her biographers, Robert Lacey, it became "the first modern event to generate media overkill."

Monaco swarmed with reporters who would have been even more excited if they had known how worried Kelly was about the medical examination demanded by the Grimaldis to determine whether she could bear children—because it would also show that she was not a virgin. (As it turned out, the matter was discreetly passed over.) Though the guests did not include a single representative from any of the royal houses of Europe, which were inclined to see the Grimaldis as quarrelsome minor aristocracy, the wedding did bring out Ava Gardner, the writer W. Somerset Maugham and Aristotle Onassis. Rainier's mother came in the company of a former jewel thief, which caused some suspicion among the several guests whose jewels were stolen throughout the week.

Princess Caroline arrived just nine months and five days after the ceremony. Albert and Stephanie would follow. Grace brought an unaccustomed American informality to the royal family. "The nursery doors were open, and the children were very much a part of the fabric of the day," says Rita Gam. But the constraints of palace life were not always easy for Grace. In 1962 photographer Eve Arnold came to Monaco to work on a CBS documentary. "I got the distinct feeling that Grace Kelly felt trapped," she says. "It wasn't the fairy tale one had expected."

To fill her time, Grace devoted herself to charities and cultural affairs, the allowable occupations of crowned heads. But her husband was against her growing wish to resume acting. When Hitchcock offered her the lead in his 1964 film Marnie, the public furor in Monaco was such that Rainier put his foot down. The part went to Tippi Hedren. "They were living in a gilded cage," says her onetime fiancé Cassini. "She wanted to be respected as an actress." By the late 1970s, Grace was spending part of each year on her own in Paris. She began to enjoy the company of younger men like Robert Dornhelm, an Austrian film director. Even as her hell-raising daughters consumed more of her time, her marriage occupied less of it.

Then came the brutal end. Kelly once told the gossip columnist Hedda Hopper, "I hate to drive a car...I am not a good driver." On Sept. 13, 1982, she and Stephanie, then 17, were returning from France along the mountain roads approaching Monaco. On a hairpin curve the Princess lost control of the car (doctors would later suspect a mild stroke at the wheel). Her Rover plunged down a 45-foot embankment, landing on its roof. She died the next day without ever regaining consciousness.

The media that had descended upon Monaco for the wedding returned for the funeral. And the royalty that had snubbed the happier occasion came this time, a recognition of the dignity that Kelly had given her role. His wife's sudden death also brought home to Rainier what he had lost. Growing old in a principality where her picture is still to be seen everywhere, the Prince, by most accounts, has been sincere in his grief. One of Kelly's favorite quotations was from the poet Kahlil Gibran: "When love beckons to you, follow him, though his voice may shatter your dreams...." In their different ways, it was a line that Grace and Rainier would come equally to understand.