The third season consisted of 22 episodes and aired between October 5, 2005 and May 3, 2006.

Three months later, things pick up where they left off at the beginning of the summer. Lucas and Peyton spent their summer together and are hiding a secret from Brooke when she returns from California and proposes a non-exclusive relationship with Lucas. Brooke takes pity on a homeless Haley and takes her on as her roommate. Haley tries to win back Nathan, who has spent the summer at "High Flyers", a bola keranjang camp, however Nathan isn't ready to trust Haley again. He pays Chris to come back to Tree...

The saat season consisted of 23 episodes and ran from September 21, 2004 to May 24, 2005.

After Lucas and Keith learn of Dan's hati, tengah-tengah attack, they return to pokok bukit and Dan decides he wants to get to know Lucas. Lucas cautiously enters into a relationship with his father. After Dan learns that Lucas has inherited his hypertrophic cardiomyopathy (HCM), the genetic defect which caused Dan's own hati, tengah-tengah attack, he convinces Lucas to alih in with him and pays for his medication, keeping his condition a secret. Dan also agrees to stay away from Keith and his girlfriend Jules (guest star, Maria Menounos)...

The fourth season consisted of 21 episodes and ran from September 27, 2006 to June 13, 2007.

As the end of High School approaches, everyone finds themselves at a crossroads in their lives. Nathan survives the accident and after some initial confusion, Haley is revealed to be pregnant while Rachel turns her attentions to Nathan after Cooper leaves town, using Nathan's theory that it was really Keith who saved him from the accident to get Nathan's attention. Rachel backs off when she learns that Haley is pregnant and Nathan later learns that he had a vision of Keith and it was this vision that...