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.

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.

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.

Now that Ryan and Seth have returned to Newport, its time to get back to school. The boys reunite with their former girlfriends but it becomes apparent that things will not be going back to the way they were. Caleb's legal troubles catch up with him, and Hailey has bad news for Jimmy.

When Sandy forgets his and Kirsten's 20th wedding anniversary, he finds himself going to a lot of trouble to make it up to her. Seth and Ryan's respective relationships with Alex and Lindsay add to the trouble, and doubt falls upon their futures together. Marissa and Julie continue to butt heads over DJ, and Summer wants to take her relationship with Zach to the next level.

As Sandy continues working on Rebecca's case, Kirsten questions how strong their feelings are for one another. Seth continues his downward spiral in the aftermath of Zach and Summer's Valentine's night together, while Marissa confronts her fear about her relationship with Alex. Caleb offers Lindsay a place in his family, but not without a paternity test.

When Ryan's brother, Trey, gets out of jail and gives Ryan a call, the Cohens give him a warm welcome. Though, Ryan knows nothing good can come from it. Zach returns from his Italy trip and gives some news leaving Summer curious and Seth ... not really sure what to think. Meanwhile, after Julie admits her naked mistake to Kirsten, they both agree to get Caleb in on it for more help. Newport Living is officially launched.

Seth and Zach squabble over who should take Summer to the prom and who will meet George Lucas for dinner; Sandy takes drastic actions with a recovering Kirsten; Ryan starts to piece together what happened between Trey and Marissa, courtesy of Theresa; Julie's attempts to poison Caleb take a surprise turn.

Jimmy must make once more the difficult decision to leave or stay with his family; Kirsten returns to the Cohen household while Charlotte has to leave her house; Marissa and Ryan face a possible separation; Taylor lords over the school musical and makes Summer and Seth her stooges.

Sandy and Matt's hospital project hits a roadblock. Kirsten and Julie run into troubles of their own with their matchmaking business. Marissa confesses her feelings to Johnny. Summer finds out out about Seth.

Harbor School's Senior Prom brings out the best and the worst in everyone. Taylor hits a high at prom, while Summer falls flat with her surprising prom date. Seth and Anna come up with a prom plan to win Summer back. Meanwhile, Marissa convinces Volchok to go to the prom and Ryan brings an unexpected old flame. When one of the girls is elected prom queen, it truly becomes a night to remember. Later, when Taylor's prom funds are missing, Ryan returns to his old ways and prom night turns brutal.

It's Thanksgiving time. Volchok is back in town and Ryan seems eager to take revenge. At first Sandy and Kirsten try to talk him out of this but, then, Sandy makes Ryan face Volchok. Julie's behavior turns Kaitlin away and permanently jeopardizes her relationship with Dr. Roberts. Summer starts protesting against poverty issues and turns the Cohens' Thanksgiving dinner into a homelesses' refuge. It's clear she hasn't got over Marissa's death yet. Veronica kicks Taylor out as soon as she discovers her beloved daughter married a French man during her European trip.

Kaitlin takes down the school mean girl by throwing a rager at her house. Sandy and Kirsten find time to bond with Ryan while Seth is away visiting Summer at Brown but all he finds is an empty dorm room. Meanwhile Julie continues work on the dating service and finds out a new surprise.