Since its very beginnings more than 80 years ago, Hollywood has excelled at manufacturing a certain kind of hybrid film. Its first half dramatizes serious contemporary issues with intelligence and depth. The last part smoothes over the rough edges and resolves everything in a sentimental mush, giving the audience a chance to cry its heart out.

Robert Redford's The Horse Whisperer is a recent example of the formula that works. It honestly lays out the emotional conflicts involved before introducing its idealized cowboy-hero. By contrast, Stepmom fails, falling between the genre's two stools of realism and sentimentality because it never confronts the key issue underlying its characters' problems: divorce. When we're finally supposed to pull out our handkerchiefs, the tears seem forced.

Director Chris Columbus (Home Alone) and his five screenwriters want to take a hard look at what are now called “blended families,” in which children live together in various combinations with natural and stepparents and try to sort it all out. Isabel (Julia Roberts), a hip Manhattan fashion photographer, falls in love with Luke (Ed Harris), a successful attorney with two kids from a previous marriage, 12-year-old Anna (Jena Malone), and 7-year-old Ben (Liam Aiken). Previously, the young career woman had “never chosen to be domestic,” but functioning as a part-time stepmother is part of her new romantic arrangement.

Isabel tries hard to be a responsible parent, but no one will give her a break. Even Luke has his doubts. Her problem is his jealous ex-wife, Jackie (Susan Sarandon), who says of her rival, “She's got the learning curve of a slug.”

The children, of course, adore their real mother. Prodded by her, they make life miserable for the new woman in their father's life. “Mommy, if you want me to hate her, I will,” Ben volunteers. Anna has already made up her mind. “She's such a witch,” she tells her dad.

We sympathize with Isabel. After she's late in picking the children up from school, Jackie tells her, “You're too self-absorbed to be a mother.” Then when Isabel takes the kids along on a Central Park shoot, Ben gets lost. This gives their vengeful mother an excuse to lay down the law. “That woman is going to have nothing more to do with my children,” she declares.

The movie presents with humor and skill the pros and cons of the long-running debate over the worth of the stay-at-home mother vs. that of the working woman. We see clearly delineated some of the conflicts between the responsibility of a family and the demands of a job. The filmmakers tilt slightly toward the choice of being a full-time mother.

Jackie is a former high-powered publishing exec who abandoned her career to become the ideal “soccer mom,” placing her children's needs above everything else. She's intensely aware that every decision she makes for them contributes to the shaping of their values and moral sensibility.

Her near perfection makes the situation almost impossible for Isabel. But as the younger woman gets to know Ben and Anna, she begins to change. At a key moment she's willing to jeopardize her fast-track professional future by rushing to their sides when they need her.

But all the adults' good intentions aren't enough. Both children want their parents to get back together, and that isn't going to happen. Ben voices their deepest fear when he plaintively asks his father, “Can you ever fall out of love with your kids?”

Anna is more direct. “You were husband and wife once,” she tells her parents. “Doesn't that mean something any more?”

Stepmom never answers this question because it cuts to the core of the changes which divorce has brought to our culture, and the movie doesn't want to challenge present-day permissive values. The parents may feel better off when they call it quits, but the kids often do not and suffer accordingly. The experience can leave a hole in their youthful psyches which may never heal.

The filmmakers try to distract us from these serious issues by a clever flaunting of some of the genre's feel-good clichés. First, everyone forgets their troubles by singing and dancing to a '60s soul tune (in this case, Motown's version of Ain't No Mountain High Enough). Next, all the remaining problems are submerged by the onslaught of a not uncommon plot twist: the disease-that-ennobles-before-it-kills.

Jackie discovers she's terminally ill and decides to put aside her differences with Isabel. Transforming herself from supershrew to saint, she works hard to achieve the transference of her children's love to her successor.

Despite these carefully calculated plot manipulations, a sour taste remains. Too much has been glossed over. Parenting someone else's children can strain a relationship to the breaking point, even when all parties are acting out of good will. And rarely does a discarded spouse become buddy-buddy with her exhusband's new partner, whatever the special circumstances. Stepmom's implicit message is that divorce is OK, and in order to get us to believe this, it must cover up the moral and psychological damage involved.

John Prizer currently writes from Paris.

Stepmom is rated PG-13 by the Motion Picture Association of America.