It's 1999, and young drug dealer Johnny Truelove (EMILE HIRSCH) rules his California neighborhood with utmost authority. Among his followers is Frankie Ballenbacher (JUSTIN TIMBERLAKE), Tiko (FERNANDO VARGAS), and their collective yes-man, whipping boy Elvis Schmidt (SHAWN HATOSY). Johnny gets his drugs from his dad, Sonny Truelove (BRUCE WILLIS), whose older accomplice, Cosmo Gadabeeti (HARRY DEAN STANTON), likes giving Johnny a hard time about girls such as Angela Holden (OLIVIA WILDE). Giving him a different sort of hard time is junkie and resident hothead Jake Mazursky (BEN FOSTER) who doesn't bow down to Johnny's authority despite owing him money.
That leads to some tense encounters between them, eventually leading to Johnny and his gang impulsively kidnapping Jake's brother Zack (ANTON YELCHIN). The 15-year-old doesn't mind, however, since his parents, Olivia (SHARON STONE) and Butch (DAVID THORNTON), have recently found his drug paraphernalia. He obviously enjoys hanging out with the older guys and smoking pot with them rather than dealing with them. Moreover, most of the drug crew -- especially Frankie -- take a liking to the kid, who's eventually introduced to others in their circle such as fellow pothead Keith Stratten (CHRISTOPHER MARQUETTE) and Susan Hartunian (DOMINIQUE SWAIN), who isn't happy once she learns Zack's been kidnapped.
With Zack's family dealing with his disappearance, Sonny tries to pressure Johnny into admitting he's involved. Realizing they may have gone past the point of no return and could face serious and possibly life-long repercussions for their act, the young drug dealer tries to figure out their best option, a choice that might not sit well with the others and especially Zack.