After fighting with his father and Haley, Nathan succumbs to the pressure he is feeling and takes amphetamines to help his game. However, he isn't prepared for the destruction the drugs do to both his body and his family. Meanwhile, Peyton goes to Lucas to rekindle their relationship, but when she arrives at his house, she catches him with Brooke.

While holding a vigil at Lucas' bedside as he lays in a coma, Karen meets her son's new girlfriend and learns from Deb that she is divorcing Dan. Most shocking of all, Karen is horrified to discover that Keith was drinking while driving at the time of the accident. Meanwhile, Nathan tries to win Haley back after she dumps him.

Lucas and Nathan bear the brunt of Dan's abuse as he coaches them into the playoffs, pushing both of them to their breaking points. Haley is stunned after Dan threatens her, causing her to reconsider her relationship with Nathan. Meanwhile, Whitey learns that his medical condition may be more serious than he first expected, and Dan learns a shocking secret from Deb.

After Lucas and Keith learn that Dan had a heart attack and is still in the hospital, they decide it is best for them to return to Tree Hill. When Deb learns about Haley and Nathan's marriage, she grows hostile. Meanwhile, angry that Lucas left Tree Hill without saying goodbye, Peyton and Brooke try to mend their friendship.

Although Nathan and Haley are already married, Tim insists on throwing Nathan a post-wedding bachelor party, while Brooke throws Haley a bachelorette party. Meanwhile, Lucas tries to decide whether he should visit Dan in the hospital. Karen decides to go back to school. Nathan gets a job working for Keith at Dan's dealership.

When Tree Hill High does a time capsule project, the gang confesses their most intimate secrets to an anonymous video camera. Nathan's anger over Haley's absence continues to grow, landing both Lucas and Nathan in jail. Peyton and Jake's feelings for each other heat up, while Felix throws Brooke a party to celebrate her new gig as student body president. Meanwhile, when brought to court, Lucas opts to live with Dan and Deb rather than Karen.

In the second part of the this seamless 2-hour Season Finale of "One Tree Hill," things heat up between Lucas and Brooke since he finally tells her what he feels about her. Nathan and Deb conspire to desert Dan for good, leading to an explosive conclusion when he discovers their plan. Peyton has a shock. Meanwhile, Karen decides to spend the summer holiday in New Zealand. And at the climax of Dan's numerous deceptions someone sets the dealership on fire with him in it.

In the third season premiere, we finally discover Dan's fate after the fire. Besides the situation with his father, Nathan also has to deal with Haley's reappearance in Tree Hill and the future of their relationship. Meanwhile, Peyton tries to find the truth about the mysterious woman who pretends to be her mother. Also, Lucas looks forward to Brooke's return after a summer apart.

It is revealed that Lucas knows who tried to kill Dan and he confronts the guilty party. Brooke, Peyton and Haley find themselves behind bars. Peyton finds her guilty conscience on the surface. Chris Keller convinces Nathan to be his wingman at a high-stakes poker game. The residents of Tree Hill finally choose a mayor.

Due to the aftermath of the release of the time capsule, chaos breaks out. Someone is holding students of Tree Hill hostage with a gun, shooting. While lives hang in the balance, Nathan and Lucas put themselves at risk to protect their friends and loved ones. Young lives are shattered and two lives will end.

The residents of Tree Hill must deal with the aftermath of the shocking accident that left everyone without words. In the midst of all the chaos, Dan extends his help to Karen now that she is pregnant, Lucas and Peyton's friendship continues to grow stronger, and once rivals Brooke and Rachel move past their differences and manage to become good friends. Brooke has a difficult decision to make about her relationship with Lucas and Skills decides to try out for the Ravens.

It's her eighteenth birthday, but Brooke soon realizes that she has no one but Rachel to celebrate it with. Meanwhile, Nathan continues to struggle with memories of the accident and Dan continues to be haunted by remorse over his actions against Keith.

As the Ravens prepare for the championship, Lucas learns Nathan intends to throw the game and decides on a risky plan to even the odds. Karen insists Deb show up for her son's final game and tries to help her get there. Also Dan makes a last plea with Daunte.

When Mouth and Rachel's road trip goes wrong, the other teens go out to their rescue. While on the trip, Nathan and Haley get a second chance to enjoy their Prom and Peyton and Lucas decide to take their relationship to the next level. Finally, Brooke reveals the truth about the stolen calculus exam to Haley.

As graduation approaches, Haley prepares for the recital of her valedictorian speech and motherhood. Nathan must adjust to life without basketball, while Brooke makes a confession that may have great consequences. Lucas confronts Dan after Karen's life is threatened.

It's four years into the future and the Tree Hill gang has finished college. Now, their lives have taken completely different directions. Lucas has written and published a book, Brooke has made it big in the fashion industry with her brand "Clothes Over Bro's", Peyton is pursuing a career in the music business, and Nathan and Haley continue to raise a now older James.

The Honorary Title performs at Tric and Mia plays her song there as well. Carrie tries to get closer to Nathan. Brooke sets Mouth up on a blind date with her assistant and Lindsey confronts Lucas about Peyton.

Lucas picks up the pieces after being left at the altar by Lindsey, while Nathan and Haley deal with the repercussions of Jamie's abduction. Dan is free for now, but he must find himself a job to convince the parole that he is changed for good. Brooke is haunted by her past as a woman from adopting asks her questions, while Peyton gets a visit from an old friend.

Lucas investigates Dan's heart condition. Haley struggles with letting Dan into Jamie's life. Peyton also still struggles with her guilt over Lucas' breakup and Mouth finally gets the chance to be a sports anchor.

Tree Hill residents are surprised to learn that a couple will indeed get married. Brooke tries to adjust to life after the robbery at "Clothes Over Bros". Nathan and Haley receive devastating news and Nanny Carrie's return creates more blanks than answers, after she kidnaps Dan - whose life is in jeopardy.

Nathan and Haley must team up to help Jamie deal with a school bully. Meanwhile, Lucas and Peyton continue to adjust to life as a live-in couple. Elsewhere, Mouth tries to get his old job back.

Peyton and Lucas deal with shocking news about Peyton's pregnancy as Brooke and Julian face a crossroads in their relationship. Meanwhile, Nathan and Haley celebrate their anniversary, with Dan and Deb babysitting Jamie; and Mouth and Millie work to redefine their relationship.

Lucas and Peyton's wedding day finally arrives, bringing some surprise guests along with it. Haley finds herself playing an unexpected role in the ceremony, as Skills and Brooke try to control Jamie and Nick. Meanwhile, Nathan continues to hope to be drafted into the NBA.

Nathan’s (James Lafferty) scandal becomes public. Brooke’s (Sophia Bush) fashion show brings an unexpected responsibility for Millicent (Lisa Goldstein), and Haley (Bethany Joy Lenz) convinces Quinn (Shantel VanSanten) to talk to her estranged husband David (guest-star Scott Holroyd”). Meanwhile, Mouth (Lee Norris) makes a decision that could threaten his career.

Nathan and Haley’s careers bring about a tough decision for the family, and Julian divulges a secret to Alex that leads to a confrontation with Brooke. Meanwhile, Clay tries to resuscitate his career as an agent, and Jamie learns the truth about Skills’ new job. And a fresh-from-jail Millie finds an unlikely supporter in Victoria.

Nathan and Haley struggle with the aftermath of her mother's death, while Brooke deals with the fallout of Alexander's tryst with Victoria. Alex discovers a secret about her leading man, Josh, that could derail Julian's film, and Clay is confronted by an unhinged Katie.

As the situation at the hospital worsens; Nathan makes a huge decision regarding his career. Brooke and Julian take Jamie for the day, while Victoria and Millicent hatch a plan.

Brooke and Julian’s wedding day is finally here. Dreams become reality, secrets are revealed and wedding hookups are inevitable.

As Nathan, Julian and Clay coach Jamie’s first little league game, the situation regarding the accident comes to a head. Meanwhile, Chase asks Alex to take a drug test for him, and Quinn gets an offer to shoot in Puerto Rico.

As Quinn distracts Jamie, Haley searches for Nathan. Clay finally gets answers about his condition. Meanwhile, Julian attempts to get back to a normal life, while Brooke tries to give Tara a chance.

Haley receives news of a possible tragedy. Dan’s search for Nathan leads him back to his dark past. Clay has a breakthrough in his treatment. Brooke and Julian deal with Xavier. Chase’s concern for Chuck pushes him to his limits.