The O.C.

Tough teen Ryan moves in with the Cohens in Orange County.

Now that Ryan's mother has abandoned Ryan and moved away, Sandy has no choice but to accede to Kirsten's wishes and remand Ryan to Social Services. Facing the prospect of living in a foster home, Ryan prepares to secretly leave on his own. But Seth finds out and suggests a better idea.

Kirsten's company does not charge Ryan with arson for the model home burning, but he must remain in juvenile hall until he can be placed in the care of a guardian.

The teens attend cotillion, where a fight breaks out.

After befriending a likeable busboy, Donnie (PAUL WASILEWSKI), at a casual seafood restaurant, Ryan takes a job there.

After a hot girl seduces Ryan, Marissa has sex with Luke.

In Tijuana, Marissa learns about the divorce and overdoses.

Ryan risks his future to keep Marissa from being sent away.

The summer is officially over, and it's the first day of school. Summer (recurring guest star RACHEL BILSON) still ignores Seth in public, but privately she is jealous of Seth's burgeoning relationship with iconoclastic East Coast girl Anna Stern (recurring guest star SAMAIRE ARMSTRONG). And Summer isn't the only person fighting feelings of jealousy. Kirsten still isn't comfortable with Sandy's fr

Marissa and Ryan date. Summer denies her feelings for Seth.

Seth gets in trouble choosing between Summer and Anna.

Anna and Summer are mad at Seth. Julie has love problems.

Seth excitedly introduces a skeptical Ryan to Chrismukkah, a Cohen family tradition that resulted from Kirsten being Christian and Sandy being Jewish.

Kirsten's rebellious 25-year-old sister, Hailey Nichol (recurring guest star AMANDA RIGHETTI), comes to town on New Year's Eve, causing turmoil in the Cohen household.

Disruptive Hailey refuses to leave. Seth chooses Anna.

When Oliver almost overdoses, Marissa stays with him.

Seth's jealousy of Summer's new boyfriend gives him doubts.

Ryan and Luke ally to protect Marissa from Oliver.

Marissa tries to reconcile with Ryan, but he can't forgive her.

Marissa and Ryan try to start over as friends, but it's not as easy as they had hoped.

When Anna plans to move away, Seth tries to stop her.

When actor Grady Bridges invites Summer and Marissa to his birthday party, the girls take Ryan and Seth to Los Angeles to join in the festivities. At the party, Summer is thrilled to spend time with Grady, but Seth is not as happy.

The Cohen family prepares for a visit from Sandy's mother, Sophie (LINDA LAVIN - "Alice"), for Passover dinner.

Marissa is mad at Julie and Luke. Caleb proposes to Julie.