The moral of Eric Rohmer's latest (perhaps last) film is fidelity to a premise, no matter how far-fetched. Those viewers girded to persevere through his reconstruction of Honore d'Urfe's 17th-century pastoral novel of fifth-century Gaul -- where shepherds, nymphs and druids flit through nondescript patches of nature discoursing on courtly love -- will be richly rewarded as pic blossoms into relaxed sensuality and humor. Rohmer's name and pic's arcane, almost perversely irrelevant premise may stir some short-term interest in urban arthouse circles, but "The Romance of Astrea and Celadon" is likely to impress more in retrospect than as a viable release.

D'Urfe's "Astree," which even the French only read in excerpts, tells the story of Celadon, a gorgeous shepherd (Andy Gillet, indeed quite gorgeous), and his beautiful beloved, the shepherdess Astrea (newcomer Stephanie Crayencour). When a jealous swain leads Astrea to falsely believe Celadon has been unfaithful to her, she banishes her lover from her sight forever. Heartbroken, Celadon throws himself into the river, from which he is saved by an upper-class nymph (Veronique Reymond) who wants to keep him for herself.

While Astrea weeps, believing Celadon drowned, Celadon sulks, stubbornly sworn to obey Astrea's injunction. A druid priest (Serge Renko) and his niece Leonide (Cecile Cassel, who enjoys pic's best ironic lines) finally persuade Celadon to dress as a woman, so Astrea will not "see" him, and the fun begins.

Until Celadon appears in drag, pic presents some rough going. As Hylas, a troubadour/fool who capers around espousing lighthearted promiscuity, Rodolphe Pauly is insufferably coy, off-rhythm and over-the-top -- particularly annoying traits in one contradicting the film's message. A long discourse that attempts to reclaim the fifth century for Christianity by transmogrifying the druid religion into the Holy Trinity, though probably a hoot when encountered in d'Urfe, makes for a woefully superfluous onscreen digression.

But pic's fantastic third act more than makes up for such occasional slogging, as Celadon, unchanged save for a close shave, braids and a bit of lipstick, forges an intimate friendship with Astrea involving hand-holding, kissing and intimate girlish sleepovers. Indeed, pic may go down in Rohmer's oeuvre as "Astrea's Breast," though peeks of knee and thigh are also on exhibit.

Though less deliberately synthetic-looking than Rohmer's "The Lady and the Duke," "Romance" often feels more artificial in its austerity. Each corner of nature appears to have been salvaged from some less bucolic landscape, and wandering shepherds might have been bussed in from Albania. On the other hand, the stilted language of courtly love feels absolutely natural. In the mouths of shepherdesses with crooked staffs and shepherds with wooden flutes, such speechifying carries the absolutism of youth -- or the intransigence of old age.

Camera (color, widescreen), Diane Baratier; editor, Mary Stephen; music, Jean-Louis Valero; production designer, Christian Paumier; costume designers, Pierre-Jean Larroque, Pu-Lai; sound (Dolby Digital), Pascal Ribier. Reviewed at Venice Film Festival (competing), Sept. 1, 2007; (Also in Toronto Film Festival -- Masters; New York Film Festival.) Running time: 109 MIN.