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 friendship with his sexy new co-worker, Rachel (recurring guest star Bonnie Somerville). Rachel makes matters worse when she specifically enlists Sandy to work on a lawsuit that an environmental group has initiated against Kirsten's father and his land development company, despite the obvious conflict of interest. Kirsten is incensed, but conflicted Sandy truly believes in the environmentalists' cause. Meanwhile in school, Marissa and Ryan become closer, but Luke is still desperate to win her back. When it looks like Luke may succeed, Ryan lets his jealousy overwhelm his reason and starts a fight with Luke. Disappointed in Ryan following the brawl, Marissa must decide whether to forgive his rage or abandon him.