Sandy comes to Ryan's rescue once again, after he has a difficult stay in Juvenile Hall. Seth makes Kirsten aware of his anger over Ryan's situation, and Kirsten makes a compromise. Ryan's mother, Dawn, makes a surprise visit to Newport, and things don't go quite as she and Ryan may have planned. The monetary secret involving Julie, Jimmy, Kirsten and Sandy comes to a head.

It's time for the annual Cotillion ball. Cherished by many, hated by most, it's the time when Newport's finest young ladies enter society. More information about Jimmy's business trouble comes to light, and Kirsten's loan to Jimmy is not happy news for Sandy.

Ryan takes a job at the Crab Shack diner. A co-worker at the diner might mean bad news for the Newport kids. Ryan asks Marissa out on a date. Sandy attempts to help Jimmy sort out his life, and gives him some bad news. Julie reveals a long-held secret to Kirsten. Disaster strikes at another one of Holly's parties.

Kirsten's father, Caleb Nichol, comes for a visit along with his new girlfriend, Gabrielle. 24-year-old Grandma Nichol has arrived. Kirsten finds her job in jeopardy, while Sandy considers making a change. Much to Ryan's disappointment, Luke decides he wants a second chance with Marissa... but who will Marissa choose? Summer makes the moves on Seth, who wonders if her feelings are real.

The Newport kids plan an end-of-summer trip down to Tijuana, Mexico (aka "T.J."). Jimmy has plans of his own, which don't sit well with Marissa. Sandy gets a new job, which Kirsten can't understand. Summer, Seth, Ryan and Marissa find themselves in a strange place together. Jimmy takes it too far. Disaster strikes one of the O.C. kids.

Everyone is back home in Newport, and Marissa is recovering. Julie points her finger at Ryan and forbids him from seeing Marissa, who does not appreciate the help. Sandy starts his new job, but finds himself surprised by the case work. Kirsten finds herself surprised by Sandy's new co-worker. Ryan enrolls at his new school, with conditions. Julie gets an intervention, and Jimmy gets a new roommate.

Couples are plentiful in 'The O.C.' It is a night of firsts. Now that they are free to love one another, Ryan and Marissa plan their first official date. Kirsten sees her father with a new woman, and fears Sandy has found a new woman of his own. Seth takes matters into his own hands with a girl, and is taken by another girl.

It's Thanksgiving time in ‘the O.C.' It's time for family reunions, and Ryan gets called home by his family. Is it because of the holiday, or is it for a favor? Marissa decides to go along for the ride, but ends up going down Ryan's bad-memory lane instead. Seth plays the player role, but not very well.

Seth and Kirsten want to avoid facing the world after their respective displays at Thanksgiving. Sandy has some advice for Jimmy, which doesn't sit well with Julie. Ryan and Luke find themselves getting along after an O.C. loved-one comes out of the closet to face negative reactions.

Ryan, and the World, are officially introduced to the bi-religious holiday Chrismukkah, thanks to Seth. And Seth insists he has TWO Godly forces helping him as he plays TWO girls. Marissa has some 'discount shopping' to do, and finds herself in an embarrassing situation, or two, or three. Kirsten does something that could cost her more than just her job. Summer and Anna each have very special gifts for Seth, but which one will he like the most? And a new boy enters the Newport scene.

It's New Years and "love" is in the air. A sister returns home, and throws a party. Oliver casts his spell. Sandy and Kirsten find themselves in a rut, and out of their environment. Seth finally makes a decision between Summer and Anna. 2004 is born.

Hailey discovers she isn't as welcome as she might have thought. Perhaps the Cohen house is full? Luke makes some new friends, while Seth and Anna try to tell a friend about their decision. Rooney sings, a lot, and Oliver noses, a lot. Trouble brews.

Oliver plans a trip for the gang, but things don't go as well as everyone might have hoped- except for Oliver of course. Summer really plants herself into "friendship" within Anna and Seth's relationship. Jimmy and Sandy decide to go into business together. Caleb and Julie return from Europe, and Hailey and Kirsten butt heads. Ryan finds himself in the cold.

Sandy and Jimmy have plans to sign papers for the Lighthouse... but is Jimmy ready? Oliver makes his plans official to Ryan, but Ryan just cannot catch a break from anyone and finds himself in an all too familiar position. Summer has a "big" new boyfriend... for a little while. And Julie gets a job.

Changes are happening within the couplehoods of the O.C.'ers. Lines seem to be blurred. Oliver reveals himself as he falls apart, but not before Ryan is completely left in the cold. Someone loses school, one loses work, two lose their partners, and one more loses it all.

It's Valentine's Day in Newport, and everyone is preparing for the Valentine's singles benefit. Luke has a new crush, while Sandy gives Seth some sex advice. An old friend of Ryan's shows up in town, which forces Marissa to lay her feelings on the table. Seth and Summer take their relationship to another level.

Ryan and Marissa begin their life together as "friends", but both discover that it might be harder to do than to say. Theresa drops into Newport for work, and another visit. Julie and Luke realize the meaning of "booty calls", and Seth and Summer make a declaration.

Anna announces that she is leaving Newport to go back to Pittsburgh, which leaves Seth feeling saddened and guilt-ridden. Legal troubles brew for Caleb and Kirsten while Sandy works to solve them. Luke and Julie's secret romance is getting harder to contain, and Theresa brings a bit of trouble from Chino to the O.C.

When Summer and Marissa run into Grady Bridges, the star of Summer's favourite prime-time soap 'The Valley', he invites them to an LA party, and they accept. On the road trip to LA, Seth, Summer, Marissa, and Ryan run into Hailey, now working at a strip club. Jimmy and Sandy present their restaurant to Newport's finest and approach Caleb for some financial help.

Nana Cohen comes to California for Passover with some sad news. Ryan searches for Marissa, who'd gone missing after learning Julie and Luke's secret, and he finds her in the most unlikely of places. Summer tries to impress Nana. Jimmy and Hailey take a step forward.

Jimmy and Sandy run into a roadblock in their effort to re-open the Balboa Lighthouse restaurant. Summer and Seth take it upon themselves to finally make Marissa feel more at home at Jimmy's. Everyone is shocked when Caleb makes a proposal, which sparks a near-fatal accident for Luke. Marissa, and Sandy and Jimmy each strike deals with Caleb. An old O.C. friend moves away.

Marissa plots to ruin her mother's happiness by inviting someone from her mother's past to the wedding shower, while Sandy attempts to hide Theresa's return to the O.C. from Ryan. When Ryan discovers Sandy's lies and Theresa's reasons for coming back, he puts himself in a dangerous situation. In the meantime, Seth's unimpressive first meeting with Summer's father leaves their relationship in doubt.

It's Bachelor and Bachelorette party time for Caleb and Julie. Caleb and the boys head off to Las Vegas while Kirsten organizes an evening at the Cohen house for Julie, strippers included. Seth and Ryan get themselves into a tricky situation in Vegas while back home, Summer pines over lost love, and Marissa comforts Theresa. Jimmy and Sandy learn of Caleb's true motives. Julie and Hailey take a swim, while Theresa has some shocking news for Ryan and Marissa.

Julie and Caleb walk down the aisle, as Ryan and Theresa face a difficult decision regarding their pregnancy. Marissa moves into Caleb and Julie's new castle on the cliff, and Seth struggles to find himself when things around him seem to fall apart. Life in The O.C. comes full circle from one year before.