Seth works at a comic book store in Newport. Kirsten drops by the store to ask Seth if he has something to send Ryan in a "care package" she is preparing. Later, Seth tries to talk Ryan in coming to dinner at the Cohens' but the latter isn't easily persuaded, saying he works nights, etc. At her dorm, Summer and a friend named Che try to rally students for a protest. Summer gets a phone call from Taylor who seems to be in Paris.
Ryan leaves Orange County to put an end to his turmoil the only way he knows how, but comes up empty on his search. Meanwhile, Seth acts like a jackass and finds some new friends in Mexico who help him find what he is looking for.
Its Thanksgiving morning at the Cohen house and the family is still dealing with what happened in Mexico. Sandy makes a deal to help Volchok but lets Ryan intervene and finally settle the score. As Summer packs to come home to be with her family and Seth, she wonders if she can deal with Newport. Meanwhile, Julie cant deal with Kaitlin or Dr. Roberts and finds herself alone for most of Thanksgiving.
Summer realizes that her trip to Brown may have changed her forever.
When Taylor learns about Ryan's sleeping problems she devises a plan to help him but must then turn to Kaitlin when her plan backfires. At Brown Summer and Che step up their activism and it lands them more freedom than imagined. Julie also gets help from Kaitlin to help save the dating service.
When Seth visits Summer at Brown, he finds an empty dorm room, and Sandy and Kirsten find an opportunity to bond with Ryan, who is in a Taylor-induced haze. Kaitlin meets the mean girl of Harbor School and takes her down by throwing a rager at the Roberts house. Meanwhile, Julie Cooper learns that Newmatch is more than a dating service and the truth about Che comes out.
After Ryan and Taylor have an accident while hanging holiday lights, they realize that everything is not as it seems in The O.C. and they will do whatever it takes to make The O.C. right again.
Its New Years Eve in The O.C. and Ryan has planned a special surprise road trip for himself and Taylor, but when Summer confronts Seth about not making any plans, Ryans romantic getaway for two is spoiled. Meanwhile, Summers future rests in the hands of a raver, the gang meets on the way to Vegas. And the Bullit asks an old friend to take a look at Julies accounting.
Kaitlin fails a class presentation and is forced to work with Will, a smart band geek at Harbor. When Kaitlin thinks she can get Will to do her homework for her, he challenges her and sparks fly.
Taylors ex-husband gets a little too close to home while he is promoting his erotic memoir. After Henri-Michel tells Ryan about Taylors exciting life in France, Ryan questions their relationship. Seth visits Dr. Roberts in Seattle to ask for permission to marry Summer. Meanwhile, Summer reconnects Holly and a vision of her future in Newport. And Kaitlin realizes she likes Will, but is concerned he thinks shes too shallow.
Kirsten is forced to clean up after Julie after one of the men she set up with a date experiences a medical condition. Will and his fellow band members have a bake sale so they can raise money to buy new uniforms.
As the Cohens prepare for Kirsten's 40th birthday party, Kirsten gets some news that will change her life forever. Meanwhile, Julie Cooper is having a secret love affair that Kaitlin does all she can to stop.
While Taylor comes up with a plan to make things right between Ryan and his Dad, Julie continues to move things forward with Bullit. But when Julie and Frank run into each other in front of Ryan and Taylor, their secret is apparent.
Ryan and Taylor share some special words but did they really mean them? Meanwhile, Kaitlin decides to sabotage Frank and Julies relationship, until her Mom finally notices and makes a change for the better. And Kirsten, for the first time, realizes what Newport society is really all about. Also, Summer encourages Seth to find something he can be passionate about. And as the night comes to a close, an earthquake hits the Southland.
After the earthquake shakes up Orange County, the gang struggles to make sure everyone is O.K. Although Sandy has told him to stay where he is, Seth will do whatever it takes to be with Ryan and Taylor.
Newport Beach has not been the same since the arrival of outsider Ryan Atwood from the other side of the tracks. In the series finale, bid the fondest of farewells and find out what happens to the Cohens, the Coopers, Ryan and Taylor.