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.

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.

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.

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.

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.

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.

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.