Kim Oja

Kirsten's rebellious sister causes turmoil by hosting a huge party in the Cohens' house on New Year's Eve. Marissa goes to another party, but Ryan rushes to kiss her at midnight.

Kirsten takes temporary custody of Ryan. Jimmy borrows money from Kirsten. Summer uses Seth for good luck at a casino benefit. Ryan's mom drunkenly embarrasses him and then leaves.

Ryan protects Seth at a party in a bad neighborhood. Ryan again must save him after Seth invites the same people to a party in Newport. Luke is shot. Broke Jimmy has a hard choice.

Anna and Summer are upset with Seth. Julie has love problems. Sandy helps Jimmy with legal issues. Kirsten's indiscretion is exposed. Ryan and Luke form an unexpected alliance.

In the fourth season premiere, everyone struggles to adjust to life without Marissa.

When Summer tries to become the gossip-loving girl she once was, she realizes that Brown may have changed her forever.