Set in the salt marshes of La Rochelle in 19th-century France (and based on a true story), "The Mystery of Alexina," a tale of doomed love, follows Alexina (Vuillemin) as she takes a job as a teacher in a small local school. She teaches the older kids; Sara (beautiful Valerie Stroh), whose sister Alexina has replaced, teaches the younger kids.

The two teachers share a bedroom, and the way they exchange glances, or the spooked expression Alexina gets when she watches Sara's silhouette through the curtain as she changes for bed, begins to suggest something forbidden. Finally, Alexina seizes Sara in an embrace; Sara recoils, and so does the deeply religious Alexina, suddenly disgusted by her own lust. The second time around, things go smoother, and pretty soon (to the gossipy delight of the schoolchildren and the school's caretaker), the two are sharing a bed.

At the time, of course, such love dared not speak its name. When the local priest and school authorities discover what's going on, they send Alexina packing. But Alexina knows . . . well, the mystery of Alexina. Armed with that knowledge, she's off to the bishop to have herself certified a man, so that she and Sara can marry.

Mostly, "The Mystery of Alexina" is one of those dreary French period pieces that depends more on atmosphere than narrative; it's a lot like "The Return of Martin Guerre," except the twists of the mystery are less adept, and there's no Gerard Depardieu. On the other hand, the movie is mercifully short (at 85 minutes), and amusing enough, if not always intentionally.

Director Rene' Fe'ret has given "The Mystery of Alexina" the stagy, overwrought feel of a silent movie, to the point of adding an inflamed organ sound track. The actors are constantly striking poses and glowering bug-eyed in the old style, particularly Vuillemin, who, with his matted hair and powdery pallor, is a dead ringer (at least in the early scenes) for John Barrymore in "Dr. Jekyll and Mr. Hyde."

The movie's oversized, self-tortured quality gives it a certain campy brio. But while the "mystery" of Alexina is explained at great length, other key plot transitions remain truly mysterious. You never really understand, for example, why the love between Sara and Alexina remains doomed, even after the mystery is solved -- you just chalk it up to 19th-century prejudice, but it would have been nice if that prejudice were illustrated or suggested somehow.

"The Mystery of Alexina" is tastefully if uneventfully shot, particularly in the way Fe'ret has restrained himself from overusing the kind of gobby, halated white light that seems to be de rigueur in this type of movie. And while Fe'ret doesn't have much of an eye, there is one long shot, of the children padding out to the edge of the ocean, their smocks white against the deep blue and gray of the water and the wet sand, in which "The Mystery of Alexina," if only for a few seconds, actually approaches cinema.

The Mystery of Alexina, at the K-B Janus, is unrated and contains nudity and sexual situations.