Kelly arrives back in Beverly Hills and reveals to Silver what happened between her and Dylan during her trip. She also confronts Ryan, who has taken a leave of absence, about the rumors that he hooked up with a student, while Ryan refuses to explain his actions to Kelly or anyone else as not to jeopardize Kimberly's undercover status to nail the drug pushers at West Beverly. On Annie's 16th birthday, Naomi sees her kissing Ethan and decides to get back at her by inviting Annie's old boyfriend, Jason, to her birthday party hoping it will break up her and Ethan, who continue to debate over keeping their blossoming romance a secret... unaware that everyone around them already knows. Meanwhile, Adrianna has dinner with Navid and his large Iranian family and she also finds out that Navid is a virgin. At the end, the big twist comes when Harry's 22-year-old illegitimate son, Sean, visits the Wilson family for the first time during Annie's party.

Navid and Adrianna fantasize about their future, but when they tell his parents about their decision to spend the rest of their lives together, things don't go as they planned when both Mr. and Mrs. Shirazi threaten to sever all ties to their son. Meanwhile, Silver tries to adjust to her new Catholic girls school, but soon learns that it is not all it's cracked up to be when her new school mate, Angela, gives her some advice to be honest about her past. Silver goes along with it... and later regrets it. While Dixon feels left out of Silver's life, Annie and the rest of the Wilsons are dealing with having Naomi as their new house guest. Naomi convinces Annie to go on a double date with Liam's friend, but Annie is shocked at the way the evening ends when Liam propositions to her. Later, Naomi's older sister Jen, who's just as brash and amoral as she, arrives in town for a visit. Naomi has no idea just how devious her sister is... and of her connections to Ryan as well as Ethan.

Following their engagement, Navid and Adrianna celebrate their respective bachelor and bachelorette parties. While Adrianna feasts with Annie, Naomi, Silver, and their female friends at the Wilson home, Liam takes Navid, Ethan, and Dixon to have a wild night on the town with some college girls at a burlesque club. Meanwhile, sparks fly between Ryan and Jen, and Dixon continues to feel unappreciated by Silver. Jen also persuades Naomi to stand up to their father as well as move in with her at a local house, while Naomi continues to grow more insecure as well as jealous over Liam when she sees him talking with Annie whom he sees as naive and holding back her own dark side.

Liam, Dixon, and Ivy learn that Naomi and Jen will be attending a horse race to watch the racehorse that Jen bought with Naomi's money, and the three of them devise a crafty and very complex plan to finally reveal the truth to Naomi about her evil sister. Ryan also tags along with Jen to the races, and inadvertently learns how Jen acquired the racehorse used to win the race. Meanwhile, Annie and Jasper sneak out to go on a Saturday date even though Harry and Debbie have grounded her for her growing misanthropic attitude. Navid wakes up in the hospital after his "accident" with no memory of who pushed him down a flight of stairs. Adrianna visits Navid and following her conversation with him, makes a life-changing decision about her addiction to pills. Elsewhere, Silver and Teddy bond over the loss of both of their mothers and unexpectedly get close to each other.

Ryan encourages Naomi to press charges against Mr. Cannon and prepares himself for the consequences. Oscar decides to set his sights on Naomi and unknowingly helps her with the case against Mr. Cannon. Ivy decides to tell Dixon she slept with Oscar. Navid and Silver attend the Achievement Awards dinner while Annie, Teddy, Liam and Ian attend The Undies, an anti-achievement ceremony at the Beach Club.

Teddy begins to feel more comfortable in his own skin and decides to visit a bar in West Hollywood where he soon realizes he forgot his wallet and is forced to turn to Ian for help. Annie is ready to take her relationship with Charlie to the next level but is mortified when his friends catch a glimpse of her in lingerie. Now a single father, Ryan turns to Debbie for help and the two end up hooking up. Navid deals with the fallout of having turned his father in for employing underage girls in his pornography business by turning to Silver. Adrianna is oblivious to Navid's situation due to her new found fame.

Navid and Dixon convince a music producer to shoot a music video at Shirazi Studios. Adrianna's suspicions are confirmed, and she tells Silver about her plot for revenge. Emily distracts Annie and tries to get close to Liam, but her plan backfires. Teddy leans on Silver for support. Meanwhile, reality producers follow Adrianna and her friends around trying to shoot a pilot, and Naomi is surprised by her reaction to a nerdy lab partner who helps her out.