Lucas and Nathan decide to return to Tree Hill after learning that Dan has had a heart attack. Deb, aside from dealing with Dan's condition, grows more enraged over Haley and Nathan's nuptuals. Meanwhile, Brooke and Peyton rekindle their friendship after lamenting their mutual betrayal by the quickly-vanished Lucas.
Lucas enlists Brooke and Peyton to help throw a surprise wedding party for newlyweds Nathan and Haley. Deb continues to be strongly against the marriage, despite the support of Haley's parents. Meanwhile, Dan attempts to repair his damaged relationships with Deb and Lucas.
Tim and Brooke decide to throw Nathan and Haley separate post-wedding bachelor and bachelorette parties. Meanwhile, Lucas tries to figure out if he should pay a visit to Dan's hospital room, and offers Nathan the chance at a job at Keith's dealership. He decides to go back to working at the cafe after Karen decides to go back to school.
Brooke is met by her brash new neighbor, who begins to make quite a blunt impact on everyone, but ends up helping Brooke out after she is busted for stealing.
Felix wants to see how far his new schoolmates are willing to go, so he sets up a "dare night" during which Lucas is enchanted by the beautiful stranger Anna. Peyton goes to church and confesses that she recently used cocaine for the first time. Keith is thrown for a loop when a woman flirts with him in the shop. Meanwhile, Karen takes a chance when she goes out with her younger professor, Andy.
In the midst of a late-night meteor shower, Lucas and Anna share an intimate night hanging out together, while Keith prepares a first-date meal for Jules, and Andy surprises Karen with a romantic dinner of his own. Meanwhile, Brooke finds herself bonding with Felix in a rule-specific "friends with benefits" relationship, and Peyton attempts to find an opening act to perform in her new club.
Karen's club opens and the whole of Tree Hill comes out to celebrate, but during the event, Lucas and Felix comes to fisticuffs over the subject of Anna.
A slumber party with Brooke, Peyton, Haley, and Anna over at Haley's apartment offers up the revelation of some dark, untold truths, along with an inadvertent crashing of the party by Felix.
Lucas takes Anna to Tree Hill High's formal dance, to Felix's chagrin, but ends up at the end of the night in the company of Brooke, who has learned the truth about Mouth's involvement with the caretaking that Felix took credit for, a truth which puts both men on the outs with her.
Nathan tells Karen about Lucas' decision to not take the test that would either confirm or deny his genetic heart condition, and a furious Karen forbids him from playing basketball until he does.
When Haley's sister, Taylor, surprises her with a visit, no one is more surprised than Nathan, who recalls her from an intimate occasion in his past. Brooke and Felix upgrade their relationship to become a dating couple, and Peyton is surprised by the return of Jake. Meanwhile, Anna trusts Lucas with a very deep and personal secret.
Nathan tells Haley about his previous relationship with Taylor, but Haley decides to keep him in the dark about her e-mails with Chris. Karen and Lucas continue to argue over whether or not Lucas should get the test on his heart. Meanwhile, Brooke tries to improve her work colleague's conditions, while Keith proposes to Jules.
A chance performance by Michelle Branch and Jessica Harp of The Wreckers forces Haley to admit to herself that music is her great passion and that she must follow the muse onto the road.
Nathan becomes an emotional wreck as his marriage to Haley falls to pieces. Karen, still mystified by Lucas' permanent move into Dan and Deb's house, tries to understand what her son is thinking. Meanwhile, sparks fly between Peyton and Jake when they have an intimate kiss, while Mouth manages to help Brooke triumph in her Student Council presidential run.
The group decides to bare their deepest secrets before a video camera in the midst of Tree Hill's emerging time capsule project. When Nathan confesses to harboring deep anger over Haley's abandonment, the results of that anger land both him and Lucas in jail.
Keith and Jules' wedding day becomes an all-encompassing affair in Tree Hill, and the enthusiasm is contagious. Brooke asks Lucas to be her date, and a remerged Nathan finally makes a major decision regarding the future of his marriage, while Peyton and Jake take another big step towards committed couplehood. Meanwhile, Karen and Andy uncover a startling revelation about a secret affair between Jules and Dan.
Keith learns that Jules was paid to sleep with him by Dan, and a very heated and physical altercation occurs between the two men. Anna learns that Felix was the one responsible for leaving the message on Peyton's locker and alerts the school. Meanwhile, Nathan decides to track down Haley and get her to come home, while Brooke and Lucas ponder her ambivalence about staying on in Tree Hill.
Traveling home from his visit to see Haley, Nathan stops off hoping for a bit of time with Taylor, with possible romantic sparks to follow. Meanwhile, Anna decides to tell her parents that she is a lesbian after her former girlfriend drops in for a visit.
Nathan and Lucas go on a racing trip with Nathan's visiting Uncle Cooper, but when the two are challenged to a race by Daytona and Garrett, an unctuous brother and sister team, the race goes horribly awry as Nathan crashes his car into a wall. Meanwhile, Dan lets Andy's class in on the secret of Andy's relationship with Karen, and Deb continues a slow, downward slide into pain medication addiction.
While unconscious after his car accident, Nathan dreams of an alternate timeline in which Dan and Karen are still married and Deb has never entered the picture, putting Lucas in the position of wealth and Deb and himself on the other end of the financial spectrum.
Nathan comes home from the hospital to find a stack of bills to pay and an eviction notice waiting for him. After a fundraiser to help him organized by Lucas, Brooke, and Peyton fails to meet expectations, Dan is the one who comes through for Nathan. Dan, however, tells Nathan that if he wants his help, he'll have to have his marriage to Haley annulled.
Brooke and Lucas go to NY to stay overnight with Haley. Dan learns that Deb and Nathan are planning to leave him. Their plan leads to a dangerous conclusion.
Brooke and Lucas go to NY to stay overnight with Haley. Dan learns that Deb and Nathan are planning to leave him. Their plans lead to a dangerous conclusion.