Ryan and Taylor may be heading out on a Las Vegas road trip for New Year's Eve, but there's even more fun in store when Seth and Summer join them. Meanwhile Julie doesn't trust NewMatch's new accountant, and Sandy suspects the reason why.

Kaitlin is assigned a tutor after she presented a ruffled report to her class. Julie comes clean to Kirsten about who Frank really is. Summer and Seth continue their recent commitment despite how they really feel about it. When Ryan's dad comes to the Cohen's for dinner things don't go as planned.

Sandy, Ryan and Seth prepare for Kirsten's upcoming 40th birthday party, however Kirsten learns some news that will change her life forever. Kaitlin tries to stop her mother having a secret love affair. Taylor visits a therapist and Ryan pretends that he doesnt miss her. Elsewhere Che finally learns that Seth isn't his soulmate.

Seth and Summer come upon a fortune teller whose prediction makes the two question whether they are truly meant for each other. Ryan gets back in touch with his father (with a little help from Taylor). When the two teens discover a love connection between Frank and Julie despite her pending engagement, a Valentine's competition is sparked between "Team Bullit" and "Team Frank". Meanwhile, with a new baby on the way, Kirsten finds herself dwelling on an old secret involving Jimmy Cooper.

It's Taylor's birthday and she hopes Ryan will tell her he loves her. She's unsure whether she should tell him she got into Berkeley as well. Summer feels that Seth should find something in his life that he really cares about whereas Kirsten is having second thoughts about raising another child in Newport. Then the unexpected happens even though it's been predicted.

In the immediate aftermath of a violent earthquake that rocks Newport, everyone struggles to stay together and keep their spirits up. Sandy and Kristen are stranded at the local shopping center where Kristen has an accident. Across town, Julie and Kaitlin are stranded in a demolished ice cream parlor on the pier with a pitiful worker of the place. Meanwhile, Ryan is seriously wounded with a piece of glass in his side, but keeps the news from Taylor to avoid panicking her. Seth soon learns of Ryan's condition and attempts to drive him to safety while Summer and Taylor search the ruins of the Roberts' house for Summer's missing rabbit, leading to Taylor having a confrontation with her mother.

The Cohen family says goodbye in the series finale as the episode jumps six months after the earthquake to show the Cohens, Ryan, Taylor, Summer and the Cooper women trying to piece their lives back together. The Cohens find out that fixing up their old mansion would cost more than rebuilding it but Ryan and Seth see this as an opportunity to give Sandy and an expecting Kirsten a surprise that'll change their lives.