The O.C.

Seth, who works at a comic book store in Newport, helps Kirsten find a gift for Ryan to include in a care package. He later attempts to convince Ryan to join the Cohens for dinner, but Ryan declines due to his night job. Meanwhile, Summer, along with a friend named Che, organizes a protest on campus, and she receives a phone call from Taylor, who appears to be in Paris.

Ryan and Seth travel to Mexico in search of Volchok, while Seth privately worries about Ryan's intentions and calls for help. Sandy and Kirsten, concerned about Ryan's emotional state, decide to follow them to prevent any impulsive actions. Meanwhile, Julie and Kaitlin deal with a mandatory school clothing drive, and Summer attempts to save a tree with her unconventional friends.

During Thanksgiving, Ryan confronts Volchok to prevent further conflict, while Julie's actions strain her relationships. Summer's activism disrupts the Cohen family dinner, revealing her unresolved grief over Marissa's death. Meanwhile, Veronica expels Taylor after learning she married a French man during a trip to Europe.

Seth's visit to Summer prompts her to reflect on how her personality has changed since attending Brown. Meanwhile, Ryan supports Taylor through her divorce, and Kaitlin and Julie attempt to avoid trouble despite facing temptation. Sandy expresses a desire for a night out with other men.

Taylor tries to help Ryan with his insomnia but turns to Kaitlin when her solution causes unintended issues. Meanwhile, Brown Summer and Che expand their activism efforts, gaining more independence than expected, and Julie also seeks Kaitlin's assistance to rescue the dating service.

Kaitlin organizes a wild party at the school's popular girl's house in an effort to humiliate her. While Seth is at Brown to visit Summer, he discovers her dorm is empty, and Sandy and Kirsten spend time connecting with Ryan in his absence. Julie makes progress on her dating service and uncovers an unexpected development.

During a Chrismukkah celebration, Ryan and Taylor are involved in an accident while decorating and find themselves in an alternate reality where Ryan was never born. As their family worries about their disappearance, the two work to return to their world with help from a letter written in the past.

Ryan and Taylor plan a New Year's Eve trip to Las Vegas, which becomes more eventful with the unexpected arrival of Seth and Summer. Meanwhile, Julie grows suspicious of NewMatch's new accountant, a concern that Sandy begins to understand.

Kaitlin is given a tutor after struggling with a class presentation. Julie reveals the truth about Frank to Kirsten. Summer and Seth maintain their relationship despite doubts, and Ryan's father's dinner visit with the Cohens leads to unexpected complications.

Taylor's ex-husband visits Newport and strains her relationship with Ryan. Seth travels to Seattle to seek Dr. Roberts' approval, Summer experiences a 48-hour trip to her past, Kaitlin begins a new romance, and Julie encounters issues with Kirsten.

Ryan makes a decisive move to win Taylor's affection, challenging Henri-Michel's advances. Che takes Seth on a journey aimed at personal and spiritual growth. At the same time, Kirsten and Julie work to address and resolve a recent family issue.

As Kirsten's 40th birthday approaches, Sandy, Ryan, and Seth make preparations, but Kirsten receives life-changing news. Meanwhile, Kaitlin attempts to intervene in her mother's secret relationship, Taylor begins seeing a therapist, and Ryan tries to hide his feelings for her. At the same time, Che comes to terms with the realization that Seth is not her soulmate.

Seth and Summer visit a fortune teller whose cryptic prediction leads them to doubt the future of their relationship. Ryan reconnects with his father with Taylor's assistance, while Frank and Julie's unexpected romantic connection inspires a Valentine's Day rivalry between "Team Bullit" and "Team Frank." Meanwhile, as Kirsten prepares for a new addition to the family, she becomes preoccupied with a long-buried secret involving Jimmy Cooper.

Taylor celebrates her birthday, hoping Ryan will confess his love, while also deciding whether to reveal she's been accepted to Berkeley. Summer encourages Seth to find a passion, and Kirsten questions whether Newport is the right place to raise another child. A long-anticipated event occurs, upending their lives.

A powerful earthquake devastates Newport, leaving residents struggling to cope and stay connected. Sandy and Kristen become stranded at a shopping center after Kristen is injured, while Julie and Kaitlin are trapped in a destroyed ice cream parlor with a frightened employee. Ryan is seriously wounded but hides his injury from Taylor, though Seth eventually discovers the truth and tries to get him help, while Summer and Taylor search through the wreckage of the Roberts' home for Summer's missing pet, leading to a tense moment between Taylor and her mother.

In the series finale, the Cohen family and their friends attempt to rebuild their lives six months after a devastating earthquake. As they assess the damage to their home, Ryan and Seth discover an opportunity to create a meaningful surprise for Sandy and a pregnant Kirsten.