Basketball lover Lucas Scott has a best friend, Haley James, who becomes involved with Lucas' bad boy half-brother Nathan Scott, whose previous girlfriend was depressed cheerleader Peyton Sawyer, whose best friend is wild child Brooke Davis.
Together, they have managed to get through high school. Even their parents have complicated relationships going on in their lives, including Dan who got Karen pregnant in high school, resulting in Lucas, until Dan met Deb and got her pregnant, thus making Nathan, and Dan's brother, Keith, is in love with Karen. But now, life have thrown everyone in a different position and place. They must now deal with...adulthood.