The car crash affects everyone's relationships: Nathan's attempt to rescue Rachel & Cooper deeply moves Haley; Brooke finally tells Lucas what she's truly feeling and Dan confronts Deb, fearful that someone has found out the truth about what happened between him and his brother.
Nathan, Rachel and Cooper continue to struggle after the accident; Brooke's 18th birthday feels hollow as she and Peyton continue to fight; Lucas and Karen bond over her pregnancy and that of another; Haley runs into trouble as the result of Deb's past.
Lucas tries to reconnect with Brooke but she denies him; Nathan continues to struggle in the aftermath of the crash; Haley tries to tell Nathan that Rachel is trying to divide them; Skills get the chance to play; Peyton bonds with her brother; Mouth laments his station in life when it comes to the ladies, but overhears a surprise; Dan is haunted by his demons.
Brooke must deal with rumors of her pregnancy spreading around town; Rachel poses for Maxim magazine; Nathan gets a motorcycle as a way of letting go of his stresses from the accident; Deb keeps intruding on Nathan's life, which prompts Haley to get involved; Lucas and Derek are at odds with each other.
Peyton discovers the truth about Derek: he's stalking her and he's not her brother. Meanwhile, a rumor that Brooke might be pregnant continues to spread; Nathan is torn between Haley and Duke University, which has just offered him a scholarship; Nathan wants Deb to try and kick her addiction.
Nathan makes a deal with Dan in order to pay the bills. The only catch to the arrangement is that Nathan might owe the man something once, or if, he attends Duke University; Lucas gets back on the team. Meanwhile, Brooke's new affair is with her teacher, and keeping it under wraps leads to some risky behavior. Peyton tries to reconnect with her brother who instead gives her "tough love." And, somebody has a crush on Mouth.
Brooke tries to juggle the fashion show and her blossoming affair with the hot teacher; Rachel winds up on the cover of Maxim as one of the Hometown Hotties and the boys at school go nuts; Lucas has to choose between Lucas and basketball; Haley has a problem with her babysitting gig; Derek tries to help Peyton overcome her anxiety by confronting her fears.
Luke has to choose between Peyton and Brooke after the former woman is urged to pursue her feelings toward him and the latter recognizes her feelings for him never went away. Meanwhile, Nathan's in a world of hurt when Daunte tells him to throw the State Championship, so he turns to the person least likely to help him out: his dad.
As the State Championship looms, the residents of Tree Hill start to feel the pressure. Peyton tells Lucas she has feelings for him; Haley learns the sex of her baby; Nathan and Lucas clash because Nathan has to throw the game; Karen shows Deb some tough love; Dan tries to deal with Daunte.
Lucas sees his dead uncle and Haley's life and the life of her unborn child hang in the balance all while Nathan struggles to come to terms with the consequences of his business relationship with Daunte. Meanwhile, Dan tries to use the car accident as a way to make amends for murdering Keith; and, Peyton and Brooke come together to stand vigil for Haley.
Lucas tries to keep his romance with Peyton alive after returning to school from his heart attack. Meanwhile, Nathan reveals to Haley the events that led to her accident; Dan complicates his defense by refusing to plead innocent to murder; Deb escapes rehab; Gigi toys with Mouth about dumping him; and, Brooke is compelled to scheme with Rachel to steal the latest calculus test.
Skills and Mouth work with Nathan to develop a plan to make some extra money so that he can buy a prom dress Haley wants but can't afford. The catch: Nathan has to take off his clothes.
A teacher gives the seniors a challenging assignment: get to know your fellow classmates. In doing so, Lucas learns that the gothic Glenda hasn't spoken to her mother in 8 weeks before confessing to her that his fallback skill after basketball is writing; Skills is worried about getting into college and opens his acceptance letter with Haley, where they both find that he will be receiving a full
Haley gets in Brooke's face when she finds out about the stolen calculus test; Lucas and Peyton grow closer as Peyton grows more comfortable with their relationship after she and Brooke become friendlier. Meanwhile, Nathan throws a house party for the Seniors, and an old videotape in his collection gets played, showing him having sex with Brooke.
Nathan tries to apologize to everyone who was offended by his and Brooke's two year-old sex tape on the day of the Prom, but he finds that proposition difficult.
It's a tumultuous prom for some of the students at Tree Hill High: Nathan and Haley must overcome a flat tire and spiked punch; Lucas discovers that his dad might have been the one who shot his uncle; and, Peyton and Brooke must fight to save their lives against Peyton's deranged stalker, Derek. Meanwhile, Rachel compels Mouth to follow her to New Orleans.
An urgent text from Mouth rouses the gang to action. In the small Texas town where he's being held, Nathan and Haley make up for their lackluster prom by attending one at the local high school; Brooke confesses to Haley that she did steal the calculus exam; and, Lucas and Peyton have sex.
Lucas tracks down the sole witness to Keith's murder and learns that it was his dad who shot his uncle. Meanwhile, Nathan fears for his basketball future; and, Peyton confronts Chase and the pain he caused her. In the process, she and Brooke become friends again.
Nathan and Haley grow closer in spite of the recent scandal. Brooke wonders if a spark might be rekindled with Chase. Peyton receives a tempting offer that would ultimately take her away from Tree Hill. Mouth reconnects with Gigi, while Lucas tells Karen that Dan is a murderer, setting off an explosive series of events.
It's Graduation Day in Tree Hill and Haley is nervous about giving her valedictorian address. Meanwhile, Nathan prepares for life after basketball, Principal Turner decides to lift Brooke's expulsion, and Lucas gets Dan to confess to Keith's death just as Karen's life hangs in the balance; and, during her speech, Haley goes into labor.
Haley and Karen deliver their babies at the same time. Karen's is a little more complicated and, in fact, her life is put in jeopardy. She has a vision of Keith, who tells her to go back and raise her child and live her life.