A disarmingly garrulous, mystery/gothic mish-mash--tricked out with Hollywood nostalgia trivia, pop-up surprises crackling through old horror-movie settings, and a heroine with the breezy brass of Myrna Loy. Young widow Laurel Warrick, a Connecticut librarian, has come to Sablecroft in St. Petersburg, Fla., a grandly eccentric castle built by late film impresario Gilbert Sablecroft as a film-history museum/funhouse. Laurel's assignment: to catalogue the stunning Sablecroft collection of books, tapes, films, and artifacts. . . while the family remains very much in residence. Regal 80-year-old matriarch Sibella, with a viola da gamba voice, queens it over the rest: her grandson Sheridan Todd; faunlike grandnephew Daniel Cavanaugh; British Pierce Poole and Wendy Abbott (both ""cousins""); and ancient housekeeper Belle McNabb. Except for Sherry, who gardens, no one ever leaves the cool castle--a temperature-controlled fantasy-land with sliding panels, winding passageways, waxworks of the great (Elsa Lanchester as the Bride of Frankenstein, Nanook in full fur, etc.), and a grand hall paced by enormous vacant-eyed dogs. Taped excerpts from golden cine-moments boom forth from various apertures, portraits, and statues. But then the fun turns sour. Someone is trying to kill Sibella (by selective shocks and a rigged, falling chandelier); Laurel, sleuthing, is also in for it; and Wendy is found stuffed in a wall. It all ends with a prolonged one-reeler chase involving a black figure in a Tibetan mask, who lures Laurel outdoors with a tape of her cat's mew--and the murderer will expire with a classic confession recorded for post-mortem listening. Great fun, especially for movie buffs but also for those who like scary-house suspense noisy with chatter and inventive incident.