Charlie Doyle, a troubled, terminally ill young man from East Chicago, has moved to Southern California with his Mom to see if he has the skills to take on the finest junior tennis players in the world. On a whim, Charlie signs up for the 1979 National Junior Tennis Championships in the Boys' 16 and under division as a qualifier. After clawing his way through the preliminary tournament, Charlie moves up through the main draw, until he finally faces Jim Chandler, power player extraordinaire, and the undefeated junior champion from Laguna Beach, California, in the 16 and Under Final.

In a heroic, crowd-pleasing display of blood and guts tennis, Charlie takes Jim to the brink of his first major loss, in what is considered the greatest junior tennis match of all-time. But Jim, somehow, barely squeaks by with a 7-6, 0-6, 7-6 victory.

But did Jim really win? After the final, Jim's lovely girlfriend, Ashley Rogers, is intrigued with the handsome challenger and begins to fantasize a storybook romance with the mythic-like, young hero.

Jim's coach and Junior Southern California USTA President, Freddy Johnson, fears for Jim's legacy in Southern California Junior Tennis and restricts Charlie from playing sanctioned tournaments because of "a few juvenile misdemeanors" Charlie committed back in Chicago.

Meanwhile, Charlie is visited by his old East Chicago High School tennis coach, Harry Moses. Harry has read about the 16 and under final and Charlie's struggles ever since. He agrees to coach Charlie full-time and help him get reinstated as a sanctioned junior player.

Harry Moses visits Freddy Johnson. Harry and Freddy were old tennis competitors back in the 1940s. But Harry smells a rat, and Freddy is exposed for taking kickbacks and bribing tennis officials.

Freddy is banished from USTA junior tennis and Jim is given a one-year suspension. During Jim's suspension and humiliation, Ashley breaks up with him and begins a romance with Charlie. Charlie experiences true love for the first time with the gorgeous Ashley, as he is now back in competition, winning tournament after tournament, becoming the number one ranked player in the 18 and under division as a seventeen-year-old.

However, during the 1980 National Junior Final in the 18 and under division, Charlie collapses on the court due to a violent seizure. It is discovered that Charlie, along with a slowly progressing hole in his heart, has a tumor that blocked oxygen to his brain, causing the seizure. After the successful removal of the tumor, Charlie begins his slow, painful recovery.

After almost a year of not playing, Charlie is determined to play competitive junior tennis once again in his last year of eligibility. Everyone is telling him he's had a great run, but now it's over. Even Ashley doesn't want him to compete anymore.

After Jim Chandler's suspension is lifted for the 1981 season, Charlie is now determined to win his rematch with the former champion. And Jim wants to prove to everyone that he is still junior tennis's greatest player, regardless of the criminal violations of his old coach. With his newfound, extreme power game, Jim is now dominating players like he used to.

But Charlie is driven, more than ever, to take down Jim Chandler once and for all.