There was this song deservedly popular some time ago, "You've gotta have heart/ Miles and miles of heart/ Oh, it's fine to be a genius of course,/ But keep that old horse before the cart,/ First you've gotta have heart." Good lyrics. Catchy tune. When you try to develop the theme of these lines into a two-hour+ movie, though, watch out. As the professor says in "One True Thing," "Less is more." What's solid for three minutes can be slender when extended. A schmltz throwback to Arthur Hiller's "Love Story," "One True Thing," based on the best-selling 1995 novel by Anna Quindlen, feels out of place in a decade devoted to edgier, wittier family dramas. We could put up with yet another soap if it worked: "Firelight" functioned because its principal performers, Sophie Marceau, left us with a solid conviction of her passion for her child and the man for whom she at first felt an unexpressed attraction. "One True Thing" lacks clarity about a singificant discovery a daughter makes about her parents, is at times difficult to believe, and trots out the usual gags about klutziness that Diane Keaton underscored eleven years ago in "Baby Boom." What is most damaging is that the picture's stated theme is not realized. "One True Thing," about a sharp, urban, 25-year-old journalist who returns to her mom and dad's New England home for a few months, promises to reveal to her a new consciousness about her parents. While she learns that her mom is a bit more noble than she thought and her dad is not the benevolent hero of her childhood fantasies, she doesn't come away with a whole lot of new perceptions about the sorts of people her folks really are.

Ellen Gulden (Renee Zellweger), a chip off her dad's block but not at all like her mom, is an ambitious investigative journalist for the hip, upscale "New York" magazine. She leaves her Manhattan digs for what she thinks is a quick birthday celebration for her New-England based father, George (William Hurt). She is commanded by this prickly 55- year-old to take a sabbatical from her job because her mother, Kate (Meryl Streep), has cancer and will need Ellen's help and presence. Whimpering at first that her career will be jettisoned by such a visit, she must accept her father's lame excuse that he simply cannot take a sabbatical at this time from his job as Am Lit professor in a top college. "You have a Harvard education," he reminds her in a guilt-tripping rebuke, "But where is your heart?"

While trying without much success to keep up with her writing via phone conversations with her young, Yuppie-ish editor, she becomes increasingly engulfed in the day-to-day tasks of caring for her mother's spiraling illness, but not before she sees the 48-year-old Kate as a woman who may be tradition-bound but devotes much of her time to fundraising and contributing her energy to good, community causes. Gaining new admiration for Kate, she is disillusioned by what she perceives as her dad's womanizing with his students, his hidden alcoholism, his shirking of responsibilities toward the deteriorating woman. In the movie's climactic scene, Kate delivers a monologue of Shakespearean proportions to her daughter, criticizing the young woman's judgmental temperament, instructing her in no uncertain terms that her standards are impossibly high and that "when you're married a long time, you make concessions."

For all its histrionics, the manifesto is lifted above the banal only by Meryl Streep's remarkable abilities as a performer. Instead of walking out on her less-than-ideal husband as she did in nineteen years ago in Robert Benton's "Kramer vs. Kramer," she has made her peace with a man whose position of authority has fashioned him into a pompous ass who breezily gives the same fatuous advice not only to students in the tutorials but to his own daughter, who is eager for genuine criticism of her writing. Karen Croner's script is virtually bereft of humor and wit, the only amusement aside from burned roasts coming from crossed wires near its conclusion when Ellen, devastated at her mother's funeral, tearfully tells her cheating boy friend "I never knew I could miss someone so much," to which the guy replies, "I missed you too." The film's frame, a conference between Ellen and an assistant D.A. (James Eckhouse) to which we return from time to time, is not believable. Since the immediate cause of Kate's death was an overdose of morphine, the D.A. is going through the motions of hearing Ellen's side of the story. The informal testimony becomes the vehicle for Ellen to narrate the entire tale, which takes her back to her father- worshipping childhood. The conference seems more like an extended psychoanalytic session: what public official would take the time to hear the story in a well-appointed office, shades discretely drawn, without the presence of an attorney or a tape recorder?

Let's admit it. We go to "One True Thing" not for the story. We've heard it all before and we're not expecting to break open the box of Kleenex this time. We're here for the acting, and we get it. Meryl Streep can do no wrong, transforming herself from a pliant, Ibsen-esque doll to an image of death itself, and Bill Hurt plays out his underwritten role as pretentious professor (is he or isn't he having an affair?). The movie belongs to the remarkable Renne Zellweger, who turns in a performance as astonishing as she did in her role in one of this year's best-acted films, Boaz Yakim's "A Price Above Rubies." She emerges as the film's one true thing.