90210 kicks off at the precise moment it ended last week: Naomi and Annie's fight is halted by the arrival of their half-brother. While Tracy shows up and embraces the son she hired a private investigator to track down, Harry is feeling guilty about all the time he missed with Sean.
We learn that Sean grew up in South Carolina and is now in the army. He ships off again in a few weeks.
At school, Naomi and Annie take every opportunity they can to go at each other. Naomi is better with the insults, as you might expect, and her self-confidence is on the rise because she's hanging out with a trio of older girls. They do make her do chores for them, however, such as program their Sidekick and get them a reservation at Ozzie's family's restaurant. In exchange for this reservation, Ozzie tells Naomi that he owes her.
Brenda, meanwhile, has owed Kelly a call back after many messages. Having been ignored, Kelly tracks Brenda down outside her latest play and schedules a lunch between the friends. At the meal, Brenda comes out and says that she and Kelly should no longer be friends. She's tired of fighting over Dylan, Ryan, etc. Then, she gets up and walks away!
Let's go back to West Beverly: at the big lacrosse game (where Annie is dressed up like the mascot), Dixon can't handle it anymore. He's sick of the attention Harry has been paying to Sean and acts out during the game, not passing the ball and causing penalties. When Harry replaces him, Dixon walks off the field with a simple: "Screw you." Back in the locker room, these two sort of make up, as it's Harry says he and Dixon will work together to help the latter feel more connected to his heritage.
(Speaking of getting screwed: Adrianna is totally knocked up! She vomits on the sidelines because she smells a hot dog. Let's keep our eyes on this likely pregnancy story line!)
Here's how the episode concludes: Because Kelly is still listed as Brenda's emergency contact, she gets summoned to the hospital after Brenda has a fall. Once there, Brenda comes clean: she slept with Ryan. Kelly is now the one that walks away from her friend.
Meanwhile, Sean unpacks his bags in the Wilson household and thanks the family for letting him crash there. After they all say goodnight, though, Sean makes a phone call, says it's all going well and everyone is accepting him - and he says all that without a southern accent...