Khloé gets a DNA test to see if Kris is her real mother, which upsets Kris. After Rob borrows Kim's car and gets a new tattoo, his unusual behavior causes concern among the family.

Scott fails to take Kourtney's pregnancy seriously, so she threatens to end their relationship. Kris upsets Bruce by not letting him buy a helicopter toy or make any financial decisions. Khloé pays Bruce to do jobs for her. Kris buys a $4000 dress for 1 event and Kim, Khloé, and Bruce play "scavenger hunt" by hiding the dress until Kris gives Bruce his ATM card to buy the helicopter toy. Rob tries to rekindle his relationship with Adrienne after seeing her at Khloé's wedding, seeming to stalk her by calling her 24/7. When he plans to visit her in New York, he receives an e-mail from her new boyfriend that informs him that it's over between them. He's heartbroken but decides to try to move on.

Dog-non-lover Kim finds herself taking in, and loving, a stray Chihuahua until she must give up "Princess" because of medical problems. Bruce pressures Rob to move out of the house, and he gets a job developing his own skin-care line with Kourtney's help.

During the one hour special, the family travels to Las Vegas to celebrate Kim’s birthday and attend an important business meeting. Kim bothered her mother for not caring about her birthday, while Scott gets violently drunk. He subsequently gets into a scuffle with his buddy, Rob Kardashian, who is also drunk. Their unruly behavior sets the tone for the remainder of the night. After Kris Kardashian is able to break up the fight, she and Kourtney think that they are able to subdue Scott and leave him in the hotel room to sober up. To everyone’s surprise, Scott shows up to the dinner/meeting where his boss is present. After using foul language, embarrassing himself and making everyone in attendance uncomfortable, Scott gets in an argument with the waiter and shoves a $100 bill in his mouth. The drama continues to unfold as Kourtney ends her relationship with Scott because of his unforgivable actions.

Scott returns to the house to apologize to Kris, but she refuses to give him another chance. Worried about never seeing Kourtney again and possibly never meeting his child, he frantically sends text and voice-mail messages until Kourtney grants him a chance to explain himself in person. She finally reconciles with him, and the whole family comes back together at her baby shower. Kim faints from exhaustion and takes 2 weeks off, deciding that when she does resume working, she won't take on so many responsibilities. After Kourtney delivers her son, Mason Dash Disick, she announces that she'll be returning to Miami to hire new girls at the store, as only 2 are currently working there. Khloé says she'll go too although she'd rather stay in L.A. with Lamar; she compromises that she won't be there 24/7. Scott is also going, to visit friends and open a nightclub. Kris is upset that Kourtney and Scott will be taking Mason along, and Bruce tells Khloé her marriage is more important than going to Miami.

A baby shower is planned for Rob and Chyna, but a fight ruins the occasion; Kris gets in an accident.