The summer is coming to an end, and Seth hasn't returned home to Newport. In the midst of home renovations, Sandy and Kirsten are strained and missing their son. Ryan has begun his new life with Theresa in Chino, as Marissa is alone and in a dark place. Summer is slowly getting over Seth.

Now that Ryan and Seth have returned to Newport, its time to get back to school. The boys reunite with their former girlfriends but it becomes apparent that things will not be going back to the way they were. Caleb's legal troubles catch up with him, and Hailey has bad news for Jimmy.

After Caleb is released from custody, he must make some decisions about the Newport Group, and his decisions don't sit well with Kirsten. Seth is determined to win back Summer's friendship, even if it means getting a job. Ryan has a string of awkward encounters with a new girl at school, while Marissa faces being alone.

It's a new era in Newport Beach. Kirsten and Julie try and work together at The Newport Group, while Sandy tries to find out what Caleb is hiding. Seth and Ryan go on a double date with Lindsay and Alex, but it ends differently than the four of them might have expected.

It's the annual "SnO.C." winter dance. Seth wants to take his relationship with Alex further, but she might have other plans. Marissa's secret relationship with D.J. is exposed, while Zach continues his pursuit of a Seth-free relationship with Summer. Sandy solves Caleb's legal puzzle ending with a shocking twist.

It's Chrismukkah once again in The O.C. and this year, Seth wants to take it global. As Caleb is faced with the looming prospect of going to prison, Sandy convinces him to come forward and reveal the truth about his involvement with Renee. Julie and Jimmy spend some quality time together. Caleb's confession shocks the Cohen and Nichol family to the core, and nothing will be the same again.

After Caleb's confession, The Cohens try to welcome Lindsay as part of the family. Jimmy is faced with a choice when Marissa finds out about his relationship with his ex-wife, Julie. Seth attempts to be a "bad boy" like Ryan to impress Alex. Summer finds out what Zach did on his Christmas break while Ryan and Lindsay want to know if it is too awkward for them to be together.

When Sandy forgets his and Kirsten's 20th wedding anniversary, he finds himself going to a lot of trouble to make it up to her. Seth and Ryan's respective relationships with Alex and Lindsay add to the trouble, and doubt falls upon their futures together. Marissa and Julie continue to butt heads over DJ, and Summer wants to take her relationship with Zach to the next level.

Seth is thrown when Alex's ex arrives in town for a visit, and is even more thrown when he finds out who it is. Julie has a plan to try and save The Newport Group, which to everyone's surprise, might actually work. Lindsay sticks out when she joins Summer and Marissa for a girls night out; meanwhile, Ryan, Seth and Zach contemplate playing it safe on a guys' night in. But nothing ever goes as planned.

Things heat up between Sandy and Kirsten when Sandy decides to help his mentor in law school find his daughter, Rebecca, whom was Sandy's first love. Seth and Zach start up a comic book based on their lives in Newport, while Summer questions why she's been left out. Ryan makes the attempt to unite Lindsay and Caleb after Lindsay tells Ryan she is curious in getting to know her "new" father. While Julie is in Paris, Marissa looks for new ways to rebel; in doing so, her friendship with Alex increases.

After hearing about Lindsay and Ryan's failed attempt at dinner with Caleb the night before, Kirsten arranges a dinner that she can supervise. But her presence makes no difference when Ryan and Caleb butt heads and disaster strikes. Sandy keeps Rebecca's presence in Newport a secret from Kirsten after deciding to take her case to court. Marissa and Alex's relationship intensifies, while Seth and Summer spend a lot of time together at Zach's insistence.

As Sandy continues working on Rebecca's case, Kirsten questions how strong their feelings are for one another. Seth continues his downward spiral in the aftermath of Zach and Summer's Valentine's night together, while Marissa confronts her fear about her relationship with Alex. Caleb offers Lindsay a place in his family, but not without a paternity test.

It's a rainy day in Newport where Lindsay decides to take the DNA test and makes a difficult choice regarding her life with Caleb while Ryan helps her through it. Sandy still wants to help Rebecca with her case and tries to convince her not to run again. Kirsten is still upset and wishes her marriage would go back to normal and for Rebecca's case to be over with. Meanwhile, Seth thinks he's lost Summer forever untill Summer is unable to hide from her feelings once and for all. Marissa moves out of the Cooper-Nichol mansion and moves in with Alex after she tells her mother about Alex being her girlfriend.

After Lindsay moves to Chicago with her mom, Ryan is heartbroken and Caleb's confused. Seth, Summer, and Marissa invite Ryan to the mall to get his mind off things. Caleb tags along to vent when Sandy tries to make amends with Kirsten by searching for her wedding ring or even a grand gesture that will take her back to when Sandy first proposed. Meanwhile, Alex learns that Marissa might not be as into her as she thought she would be. Kirsten and Julie call an editor for Newport Living but at the same time Julie's Riverside past catches up to her.

Spring has flung in Newport where Marissa recruits Ryan to help her with Harbor School's Pep Rally Bonfire. Alex accepts that her and Marissa are from two different lives and knows she is fighting a lost cause. Seth is stuck and misses last year's good times while Summer disagrees and tells him it's time to move on. Meanwhile, Julie still doesn't know what she is gonna do about her blackmailer and seeks some advice from Sandy. Kirsten wants Carter to stick with the magazine despite his reservations.

Cohen ailesi, Ryan’ın Chino günlerinden gelen ziyaretçisine samimiyetle kucak açar. Ryan ise geçmiş günlerinden iyi bir şey gelmeyeceğini düşünerek endişelenmektedir. Marissa ve Ryan ilişkilerini yeniden şekillendirirken, Seth ve Summer ise beklenmedik haberlerle yüzleşir. Bu arada Julie, Kirsten’a yaptığı hatayı itiraf eder ve Caleb’in desteğini bekler.

Newport grubunun fahri başkanlığına getirilen Sandy, Newport’la ve zorlu işleriyle ilk kez karşılaşan Trey’den yardımını rica eder. Sandy Newport’un icrasını ertelemeye uğraşırken, Kirsten ve Carter şirketin sahip olduğu demirbaşların satılacağı müzayedede aynı masayı paylaşır. Bu arada açık arttırmanın en değerli parçasının kaybolduğunu farkeden Seth ve Ryan biraz yardım alarak durumu çözmeye karar verir. Trey ise sürekli kalabileceği bir yer aramaktadır.

Trey ve Ryan’ın ilişkilerini düzeltmesini çok isteyen Marissa, Caleb’ın evinde Trey için bir doğum günü partisi düzenler. Ne yazık ki parti kısa sürede kontrolden çıkar. Carter’la yaptıları sörf gezisinden sonra Sandy, Kirsten’i hayal kırıklığına uğratacak bir teklif yaparak Carter’ı bir bayan arkadaşıyla tanıştırmayı önerir. Bu arada Summer, Seth’in çizgi romanının olası yayımcısı Reed’in gerçekte neyin peşinde olduğunu farkeder. Seth’in başı büyük beladadır.

Caleb’ın malikanesindeki hareketli partiden sonra Sandy, Seth ve Ryan, Trey’in hapse girmesini önlemek için işe yarar bir plan yapmalıdır. Kirsten ve Carter iş için şarap ülkesine doğru kısa bir gezintiye çıkar. Bu arada Caleb Avrupa’dan döner ve Julie’nin romantik girişimlerine olumsuz cevap verir. Bu bölümde Death Cab Cutie’nin performansını dinliyoruz.

Sandy, Seth ve Ryan; Seth’in Miami Beach’te yaşayan büyükannesi Sophie’yi ziyarete gider. Burada tanıştıkları Mary Sue, Seth ve Ryan için hayal bile edemedikleri insanlarla tanışmaları için anahtar kişi olacaktır. O.C’de ise Carter her şeyini toplayıp giderek Kirsten’i ofiste bir başına bırakır. Bu arada Trey, Marissa’nın arkadaşlığını yanlış yorumlar.

Carter’ın ayrılmasından sonra Kirsten’in davranışlarının tuhaflaştığını fark eden Sandy, karısına her şeyin yolunda olup olmadığını sorar. Aldığı cevap yatak odasında yalnız kalmak olacaktır. Etrafında Marissa’nın agresifliğini fazla hissetmeye başlayan Ryan, Trey’le eski kız arkadaşının arasında bir şeyler olduğundan şüphelenmeye başlar. Summer ise Seth ve Zach’in aptalca davranışlarından usanmıştır. Bu arada Caleb, Julie’ye çok şey anlatan bir resim gösterecektir.

Sandy ve Caleb, Kirsten’ı son zamanlardaki davranışlarıyla yüzleşmek zorunda bırakır. Ryan ise Marissa ve Trey arasında geçenleri öğrenmek için Chino’ya gider. Bu arada Summer, Seth ve Zach’le aralarındaki tuhaf ilişkinin mezuniyet balosuna katılmasını engellemesine izin vermeyecektir. Julie ve Caleb ise karı-koca olarak geçirecekleri son geceyi kadeh kaldırarak kutlar.

Sandy evliliğini kurtarmak için hayati önem taşıyan bir karar vermek zorunda kalır. Seth, Summer, Marissa ve Ryan ‘’Beat Shop’’ta çapraz ateş altında kalacaklardır. Kızı Marissa ve ailesi hakkında endişelenen Jimmy Cooper ise Newport’a ani bir dönüş yapar.