It is common nature to eventually repay someone who does a good deed for you. But what if, in a perfect world, that very act of kindness led you to, instead, pay that very good will to three other people, under the condition that they will do the same for three more? Idealistic? Yes. But that is the key notion present in "Pay It Forward," a brilliantly acted, but dramatically inaccurate drama, saccharinely directed by Mimi Leder (1998's "Deep Impact"). There is rarely a kind of film more disappointing than those that strive for excellence, and have what it takes to be successful, but come up far short, misplacing emotional honesty with audience manipulation. For every moment of true poignance and effectiveness, there are three that ring with a resounding falseness that stops the whole picture in its tracks.

It is the first day of the seventh grade, and intelligent latchkey kid Trevor (Haley Joel Osment) is intrigued when his hard-edged, but caring, social studies teacher Eugene Simonet (Kevin Spacey), whose severe scars on his face mask his fear of ever getting close with anyone, presents the class with an extra credit assignment--find a way to change the world, and put that idea into play. Whereas the rest of his classmates choose to begin recycling and picking up trash alongside the road, Trevor takes the assignment very seriously, devising the idea of paying it forward, in which you do something important to change someone's life with the understanding that they will do the same for three other people, and those three do the same for three more, and so on.

Trevor's first act of kindness is taking a heroin-addicted homeless man (James Caviezel) off the streets and giving him shelter in his garage, unbeknownst to his working-class mother, Arlene (Helen Hunt), who rarely gets to see Trevor, as she works two jobs (one at a Las Vegas casino, and the other as a waitress) and drinks herself to sleep every night. Arlene loves Trevor unconditionally, but he holds her in contempt for her dishonesty about her alcoholism. With the fear that his no-good, abusive father (Jon Bon Jovi) will eventually come crawling back to her, Trevor next decides to set Arlene and Mr. Simonet up, in hopes that both of their inner pain and suffering will make them a perfect match for each other.

Meanwhile, set four months later, Los Angeles news reporter Chris Chandler (Jay Mohr) gets his car totaled, only to have a kindly man give him a new Jaguar, no strings attached. This unbelievable financial sacrifice leads Chris to discover the Pay It Forward Movement, which he eventually tracks all the way to Las Vegas, where Trevor resides and has no idea his idea has spread across the country.

Based on the popular novel by Catherine Ryan Hyde, "Pay It Forward" intermittently succeeds solely due to the powerhouse performances from the three leads. After all, they get no help from the uneven screenplay, by Leslie Dixon, which is unconvincing in its romance between Arlene and Eugene, a subplot that gradually becomes the center of the movie. Had the emotionally wounded Arlene and Eugene struck up a friendship and, together, helped each other to come to terms with the problems and mistakes that they had made in their lives, the film would have been infinitely more effective than the melodramatic, totally unnecessary romance that comes to the forefront.

Kevin Spacey (1999's "American Beauty") and Helen Hunt (2000's "Dr. T and the Women") are well-cast as the conflicted Eugene Simonet and the struggling Arlene, respectively. Both actors are at the top of their games here, with Spacey always lending an assured, realistic presence to his roles, and Hunt never being better. Hunt, especially, has gone all out to present us with a decidedly unattractive portrayal of a woman who is torn between the love for her child and the addiction to alcohol that she can't seem to kick. Never once afraid to look physically worn-out and wretched, Hunt gives a brave and touching performance, one of the very best of the year.

In his first cinematic venture since his Oscar-nominated turn in 1999's "The Sixth Sense," 12-year-old Haley Joel Osment is nearly flawless. Unlike the vast majority of child actors, who are too precocious for their own good, and whom you can always catch acting for the camera, Osment delivers such unaffected work that he even puts to shame many A-list adult actors. "The Sixth Sense" wasn't at all a fluke; Osment is the real deal.

The supporting players run the gamut from emphatic to misguided. Angie Dickinson (2000's "Duets") is a standout as Arlene's mother, a bag lady who is surprisingly satisfied with where her life is at, or just comes off that way to hide her pain and regret as both a mother and a person. Jay Mohr (1999's "Go") can be a fine actor, but his role of reporter Chris Chandler, who tracks down the source of the Pay It Forward Movement, is utterly superfluous, and every time his scenes show up, you can't help but think how this whole subplot slows the main story down, and could have been edited completely from the movie without making the slightest bit of difference. Finally, James Caviezel (2000's "Frequency") does what he can with his few scenes, while Jon Bon Jovi (1998's "No Looking Back") appears in little more than a cameo.

The concept of paying it forward is surely a fresh one, and although it probably would never work in the real world, the movie remains hopeful and strong-spirited. What is so disheartening, then, is that its reliance on plot contrivances keep weighing down all that is good about the film. Additionally, the downbeat ending is nearly unforgivable, (minor spoiler ahead ) sparing one of the characters' lives for the sole purpose of getting the audience to grow weepy. Had the death been the least bit respectably or realistically done, then it might have been all right, but the approach that is taken comes off feeling like a thoroughly artificial twist. It puts the final nail in the coffin of "Pay It Forward," an already-flawed motion picture that could have added up to so much more than it ultimately does.