The O.C.

The friends begin their senior year, but the cops want to know who shot Trey. Ryan tries to protect Marissa. In rehab, Kirsten makes a friend who may not be trustworthy.

Sandy frets over Kirsten's attachment to her rehab friend. Marissa gets bad news from the new dean. Summer trumps Taylor when planning a carnival. Jimmy makes a proposal to Julie.

Julie and Sandy keep Ryan and Marissa apart, but Seth and Summer help them enjoy a night to remember. Taylor catches them in the act. Caleb's will disappoints Julie and Jimmy.

Marissa adjusts to a new school. Ryan wonders if their separation will affect their relationship. Seth's feud with Dean Hess gets Summer in trouble. Charlotte arrives in Newport.

Ryan makes a life-changing decision with Sandy's support. Dean Hess tries to ruin Ryan's future, but Summer and Seth know a secret about Hess. Charlotte makes Julie an offer.

Taylor ruins Seth's night by keeping Summer away. Marissa's new friendships at public school worry Summer. Sandy forms a new partnership. Charlotte manipulates Julie and Kirsten.

During a show by rock band THE SUBWAYS, Taylor's behavior causes a major rift between Seth and Summer. Marissa is determined to end the conflict between Ryan and Volchok.

The friends plan their futures. Marissa attends Johnny's surf competition instead of completing her college application. Julie is forced to return to her roots.

Ryan works an internship for Sandy. Summer and Seth try to impress Brown University. Johnny reveals how he feels about Marissa. Ryan and Marissa tell each other the truth.

Somber Summer misses her mom. Johnny's misfortune forces him to take action. Kirsten tries to make amends with Julie. Seth invents another holiday.

The friends try to get Marissa back into their school. Sandy makes a decision that could change Marissa's fate. Summer's father and Julie have been lying to their daughters.

Marissa's sister, Kaitlin, returns home with attitude and a few secrets. Much more in the mold of Julie than Marissa, Kaitlin turns heads as she tries to get closer to her family.

Kaitlin stirs up trouble for the gang as she prepares to celebrate her birthday. Sandy encourages Seth about college, but Seth finds a better alternative.

Summer discovers the truth about Seth. Kirsten and Julie take their matchmaking business too far. Marissa tells Johnny how she feels. Kaitlin wonders which Cooper he really likes.

Tragedy strikes the friends. Johnny's cousin arrives. Ryan questions his and Marissa's relationship. Kaitlin leaves. Kirsten and Julie plan a Valentine's Day party.

Sadie and Ryan go on a road trip to find one of Johnny's relatives. Ryan returns to his old ways. Marissa is implicated in Johnny's death. Seth and Summer discover Julie's secret.

Ryan struggles to decide whom to invite to his birthday party. Julie and Dr. Roberts come clean with Summer and Marissa. Ryan and Sadie grow closer.

Ryan's nemesis returns to Newport. Taylor tries to solve Seth and Summer's problem. Marissa is all alone in Newport. Sandy grapples with business pressure.

Julie and Dr. Roberts announce their engagement. Marissa seeks solace with bad boy Volchok. Ryan tries to move on with Sadie, but Seth's concern for Marissa gets in the way.

The kids receive their college acceptance and rejection letters, forcing them to make decisions. Ryan and Sadie decide what do after high school. Marissa and Summer reconcile.

Ryan visits his mom. Taylor and Summer wonder why Seth is keeping secrets. Julie gives Volchok stern advice. Marissa confronts Volchok's friends and saves a girl.

The friends go to their college orientations. Seth sees Anna at Brown, and they instantly connect. Kirsten and Sandy attend a hospital benefit where Kirsten vents her frustration.

The senior prom brings out the best and the worst in everyone. When Taylor's prom funds are discovered to be missing, Ryan returns to his old ways, and prom night turns brutal.

Ryan makes a deal with Volchok. Marissa visits Kaitlin at boarding school. Ryan forces Theresa to make a difficult decision. Seth's actions ignite even more trouble in Newport

The end of senior year brings the excitement of graduation and the anticipation of new lives in college and beyond. Seth confronts his recent misdeeds. Ryan's proud mom arrives.