尤金·賽門特（凱文·斯帕西飾）是一位善於把生活安排得井井有條的社會學教師。阿琳·麥肯尼（海倫·亨特飾）是一位生活拮據的單親媽媽，為了撫養兒子特維（海利·喬·奧斯蒙特飾）而沒命地工作，借酒澆愁是她的唯一“愛好”。
這一切在這一天發生了改變，尤金給特維的班級布置了一道特殊家庭作業：讓世界變得更美好。特維決心從自己做起，因為他相信做善事一定會有善報，於是他把無家可歸的流浪漢請到自己家……
在特維的感召下，人們從起初的猜疑、嘲諷逐漸地表示認同，大家驚訝地發現自己在付出愛心的同時，也在得到別人的幫助，這個世界真的可以變得更美好！
Based on a best-selling novel by Catherine Ryan Hyde, and boasting the star-power of three prior Oscar winners--Kevin Spacey, Helen Hunt, and Haley Joel Osmont--PAY IT FORWARD spins a heartwarming yarn about an eleven-year-old boy who comes up with an utopian idea as a project for school. History teacher Eugene Simenot (Spacey) offers the same ongoing extra-credit assignment he has proffered every year: Come up with an idea that will change the world. However, he expects nothing more from his students than half-hearted efforts that fall far shy of their mark. Simenot is therefore unprepared for precocious, irrepressible Trevor McKinney (played with wide-eyed wonder by Osmont), who conjures up a stunning scheme. Trevor suggests the concept that every person who benefits from someone else's good deed should "pay it forward," instead of paying it back, and in turn offer favors to three other people. The first guinea pig for Trevor's experiment is his overworked, imperfect mom (Helen Hunt) for whom he tries to find a boyfriend.
Director Mimi Leder, best known for powerful thrillers like DEEP IMPACT, imbues the solid script of PAY IT FORWARD with a more grandiose aura. However, it is the movie's triumvirate of heralded stars--Spacey, Hunt and Osmont--who propel this compelling yarn.