Anna announces that she is leaving Newport to go back to Pittsburgh, which leaves Seth feeling saddened and guilt-ridden. Legal troubles brew for Caleb and Kirsten while Sandy works to solve them. Luke and Julie's secret romance is getting harder to contain, and Theresa brings a bit of trouble from Chino to the O.C.

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.

Sandy reluctantly serves as host/auctioneer at yet another OC benefit; Trey lies to Ryan to prove that he can be self-dependent; Carter reinvigorates Seth and Zach's comic book dream, much to the annoyance of Summer. Marissa moves in with the Cohens.