She was the perfect Hitchcock heroine -- classy, cool and distant, but as he put it, also the embodiment of "sexual elegance." When she left Hollywood to marry Prince Rainier in 1956, he was never able to replace her.

Grace Kelly, who died yesterday at 52, was always irreplaceable, and her fans knew it. Under her aristocratic beauty there was dramatic talent. She won the Academy Award for "Country Girl" in 1954. She made only 11 movies, but there was always the possibility of one more.

In one of her last interviews, in the September Ladies' Home Journal, Princess Grace said she remained close to many friends from her Hollywood days, and confirmed that she had been offered either of the leading roles in "The Turning Point."

Although she declined, she said she still had her original makeup kit, occasionally gave dramatic readings and did not rule out public performance in the future.

Her appeal was no secret, of course. She was absolutely beautiful in the most rigorous application of the word. She was immaculate, she was perfectly groomed, she could wear white gloves. She was, in a sense, a first-generation American beauty. Her father was a self-made millionaire from Philadelphia, and she was the daughter who could do no wrong.

Her sex appeal was indirect and quite suited for the years 1951 through 1956, during which she had her entire movie career. Perhaps this was what Hitchcock noticed, and why he cast her in "Dial M for Murder," "Rear Window" and "To Catch a Thief." His comment perhaps said more about himself and his audiences than it did about Miss Kelly, but it rang true:

"You know why I favor sophisticated blondes in my films? We're after the drawing-room type, the real ladies, who become sexy once they're in the bedroom."

There were only hints of passion, of course, but in the way of Hollywood in that period they were marvelously effective. In "Rear Window," she was wearing a pink chiffon negligee when she murmured to James Stewart, "Preview of coming attractions."

In "To Catch a Thief," she proposed to Cary Grant a choice of leg or breast. She very convincingly proved irresistible to Clark Gable in "Mogambo."

She was lovely, she was aristocratic, but she was not the sort of star that teen-agers imitated as they did Elizabeth Taylor, and she did not start trends in haircuts, as the late Ingrid Bergman, who was her friend, did in "For Whom the Bell Tolls."

You could admire Miss Kelly, you could wish to be Miss Kelly, but any imitation seemed vulgar and doomed to failure. She was royalty from the beginning, and everybody knew it. It came as no surprise that Prince Rainier noticed it too.

This quality shone through any role. Her second film was "High Noon" with Gary Cooper, in which she played a well-dressed lady of the Old West in whose bonnet no hayseed could ever have lodged itself.

In "Dial M for Murder," she managed to kill her would-be murderer with a pair of scissors without really getting mussed up in the process.

She played a wife well, whether as the spirited Quaker of "High Noon" or the military spouse of "The Bridges at Toko-Ri." In that film of 1954, William Holden was a carrier pilot living with the specter of his own death, and as he tossed and turned in their bed she looked at him with a detached compassion of almost classical nature.

Edith Head, the costume designer, recalled that she "had the look of a star the first time I saw her. She was immaculate, from her well-groomed hair to the fresh white gloves which would become her trademark. She had a flawless figure, and with her modeling experience, she was the perfect subject for my designs."

Her last films are the closest we have to autobiography: She portrayed a princess in Charles Vidor's "The Swan," and the daughter of a wealthy Philadelphia socialite in "High Society," both in 1956.

During the 26 years that followed her departure to Monaco, her public appearances were carefully orchestrated. The suggestion was of a continued aloofness -- an admirable disinclination to enter the public confessional visited by many of her peers.

From time to time, however, she gave interviews, and in one of them she was asked by a cloying questioner if she was "truly happy."

"Well," Princess Grace replied with what seemed more like wisdom than regret, "I don't believe that any of us is ever truly happy."

She was beautiful when we knew her, and as a princess she became wise.

It seems that, all along, she was what she appeared to be.