'Tis the season of emotionally manipulative movies, this winter of 1998-99.

Starting on Christmas day with "Stepmom" and "Patch Adams," the major studios have served up several movies that shamelessly, and often insincerely, strip-mine out tear ducts for every drop of moisture they can muster.

The second wave of this incursion started Valentine's weekend with "Message In a Bottle" (widower Kevin Costner learns to love again) and this week the siege continues with "The Other Sister," the soft-hearted story of a mentally challenged young woman learning to support herself and falling in love.

Now I admit to being a cynic by nature, but I also have a soft spot the size of a small city when I'm not being shot in the face with a payload of pathos.

Having said that, "The Other Sister" is the most sincere, unregulated and honestly sentimental picture so far in this crop of sappy cinema.

Co-written and directed by Garry Marshall (who knows from sap -- he directed "Beaches") and starring Juliette Lewis as Carla Tate, the slightly retarded daughter of San Francisco socialites Diane Keaton and Tom Skerritt, "The Other Sister" is the kind of movie that threatens to turn tragic or melodramatic at any moment. But, in a refreshing change, it never does.

The story follows Carla as she returns to her family after a 10 years at an upscale care home and school. Her reintroduction to family life is awkward, as her controlling and ultra-edgy mother attempts to shelter Carla while trying to make up for a decade of distance by "treating" her to mandatory tennis lessons and shopping sprees.

Carla, of course, has other ideas and enrolls in community college, where she meets Daniel (Giovanni Ribisi), a similarly challenged fella with a job (cookie maker at a bakery), a small apartment and a penchant for the music of marching bands.

Now filled with like ambitions and falling in love to boot, Carla begins to assert herself as a capable adult, pulling against her mother's newly-rediscovered and steel-belted apron strings.

The best thing about "The Other Sister" is that the script, once it gets past the obligatory mean kids at school, isn't filled with the kind of pre-fabricated obstacles and crises a story like this invites. The focus is on Carla's self-motivated growth instead of on how she overcomes those who would hold her back, and writer-director Marshall show up people like me, who often go into this kind of movie expecting to roll our eyes endlessly.

The movie's packaging, however, leaves something to be desired. While it's extremely well paced, a seemingly endless stream of musical montage sequences frequently substitute for substance -- especially when it comes to Carla and Daniel spending time together -- and it is peppered with many, mostly forgivable, slips in common sense.

As Carla and Daniel move toward a possible marriage, Marshall's script becomes more mechanical, punching up the story with predictable points of tension. He also gets a little generic at times, writing one of Carla's sisters as the token Hollywood lesbian in Donna Karan suits, perfect makeup and a carbon copy girlfriend (no dykes allowed). And in the third act he falls back on one of those movie weddings (not Carla's) that exist in the plot only so someone can make a scene.

Lewis and Ribisi give accomplished performances, lending Carla and Daniel depth, dignity and strength of character that rallies the audience behind them early on. In fact, everyone in the cast is uncommonly natural, especially Skerritt as the devoted father who insists on giving Carla a chance to prove herself.

Only poor Diane Keaton is stuck in a wildly inconsistent role as a shrewish flake of a mother who waffles exhaustingly about her daughter's independence. But she still manages to come off sympathetically once she stops throwing fits.

"The Other Sister" doesn't try to be a three-hankie movie, like its recent rivals, and that's why it doesn't disappoint, even if it is far from perfect.

By the way, the attack of the tear-jerkers isn't over yet. On March 12, Michelle Pfiffer plays the mother of a missing child in "Deep End of the Ocean," which may be the most insistently mawkish of all the movies mentioned here.