The idea of faded luster is central to "Fedora," a pedestrian mystery melodrama about the secret of longvity guarded by a reclusive, legendary screen beauty (Fedora) who somehow contrived to sustain her career as a romantic idol for over four decades.

It isn't surprising that Billy Wilder perceived an exploitable variation on his own "Sunset Boulevard" in a portion of Thomas Tryon's book "Crowned Heads."

Unfortunately "Fedora," now afforded a belated local showing at the Capitol Hill and K-B Janus, is decidedly inferior to Wilder in his prime. The sight of William Holden gamely struggling to bring conviction to a weary echo of his role in "Sunset Boulevard" serves as a constant invitation to unflattering comparisons. Nevertheless, "Fedora" has a certain fascination. It fails as a self-contained work, but confirmed movie nuts may find it a curiously evocative and even appealing wreck of a picture.

Wilder and his screenwriting collaborator, I.A.L. Diamond, have fabricated a grandiose, prolix screenplay revealed to be a structural disaster: fWhen the story appears to be only seconds away from fadeout, the audience is asked to sit still for another two reels.

Having depicted the strange case of Fedora from the point of view of an intruder who stumbles upon her secret Holden as a desperate, importuning movie producer called Barry Detweiler who journeys to her retreat on Corfu in an attempt to coax her into a comeback with an adaptation of "Anne Karenina" -- the filmmakers are not content to let a fundamentally weak mystery rest in peace. They switch narrators and begin doggedly documenting the cast from an insider's point-of-view that is introduced too late to be anything but anticlimatic.

Tryon's story was a misleading mixture of clements of the Garbo legend with elements of Herman Melville's "Benito Cerrino" and Evelyn Waugh's "The Man Who Loved Dickens." Tryon's original story could use a lot more in the way of suspense, surprise and character delineation, and it's natural to assume that it might be told more forcefully if one could get inside and concentrate on the ambiguous relationship between Fedora, played in the film by Marthe Keller, and her aged, infirm hostess-mentor, the Countess Sobrianski, portrayed by Hildegard Knef. The movie adds a good deal of fresh incident, dialogue and characterization, but the outline remains the same.

Upon arriving in Corfu, Holden's character snoops around the Countess' villa, is refused entry, makes contact with Fedora during a chance encounter in town, ingratiates himself by loaning her money (for a consignment of drugs) and begins to suspect that her melodramatic accounts of being mistreated and held against her will at the villa may not be sheer paranoid delusion.

Despite its weakness, the movie possesses fleeting evocative appeal. Although his storytelling sense has become slack with advancing age, Wilder can still get in some characteristic funny strokes, particularly on the subject of the movie business.

For example, when Mario Adorf, who gives a wonderful performance as a cheerful, gossipy hotel manasger, helpfully suggests that Holden sneak his script into the villa via the butcher.

"He can wrap it up in the meat for the dogs" the mocking sense of humor behind this innocent remark is unmistakable. The same is true of a scene in which the producer answers the Countess' objection that "Anna Karenina" has already been done twice with Garbo by cracking, "So what? This time we can do it right," and of the Countess' subsequent criticism of "Anna Karenina" itself on the grounds that no real lady would ever commit suicide by throwing herself under a train. Wilder hasn't entirely lost his sarcastic tone, and a movie that enjoys the collaboration of distinguished scenic and atmospheric artists like designer Alexander Trauner, cinematographer Gerry Fisher and composer Miklos Rozsa isn't exactly ready for the junk heap.

Wilder has had a substantial career, and even when faltering, he draws on substantial reserves of talent. His film will find a more secure eccentric niche in the annals of American movies than Tryon's "Fedora" will in the annals of popular fiction.