The tension between Lo, Lauren and Audrina continues and soon things reach boiling point.

Stephanie's birthday party is around the corner and so everyone tries to make an appearance. Also things start to change for Whitney.

Whitney's love life starts to heat up while Lauren's starts to cool down. Meanwhile Heidi and Spencer fight.

A blowout trip to Las Vegas turns sour when Audrina snubs Lauren, Brody brings up Stephanie's past and the boys end up in jail.

Brody is still in jail, so the girls try to come up with a way to get him out. Plus Audrina and Lauren finally sit down and talk to each other.

Holly reaches out to Lauren, forcing Lauren and Heidi to reconsider their friendship. Meanwhile, Audrina and Justin's relationship is tested.

When Lauren is away for a couple of days, Stephanie and Doug start dating secretly. How long will that stay a secret though?

Doug and Stephanie have to explain themselves to Lauren. Meanwhile Heidi's mother pays a visit.

Heidi tries to reach out to Lauren. Meanwhile Audrina has a date, but what will Justin say to that?

Spencer sets an ultimatum for Holly to move out. Meanwhile Audrina checks which boy is best for her. Will it be Justin?

Lauren and Audrina travel to Cabo for Brody's birthday, but Audrina's problems with Justin threaten to ruin the festivities. Back in LA, Spencer gives Stephanie's new boyfriend a hard time over dinner.

Audrina suprises Lauren when she moves out, and Heidi disappoints Brent Bolthouse when she invites Spencer to a work event and gets caught having a little too much fun.

Whitney finds romance when she and Lauren head to New York City for fashion week. Back in L.A., Spencer makes things worse for Heidi by approaching Brent to ask for her job back.

Heidi decides to go back to Brent and Sam and ask for her job back. Plus, Holly Montag's crashing at Lauren and Lo's since getting kicked out of her sister's place.

A nasty rumor threatens to end Lauren and Audrina's friendship and Heidi realizes Spencer's been withholding information from her.

Audrina tries to make amends with Lauren after the fall-out. Then it's off to Nana's house where Spencer and Stephanie compete for their grandmother's affection.

In NYC, Whitney has an interview with Diane von Furstenberg and sees Jay. Plus, Lauren says goodbye to her Laguna home and Stephanie makes a difficult decision about Cameron.

Spencer and Heidi ignore the concerns of their families and elope in Mexico. Meanwhile, Whitney says goodbye to Lauren and her life in Los Angeles as she leaves for her dream job in New York City.

The season four finale finds Lauren and Heidi running into each other and are reminded why the once were best friends. Meanwhile, as Heidi's mom pays a visit, the she and Spencer know they must face reality; and Audrina is surprised by Justin with a trip to Palm Springs.