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.

Kourtney, Kim, and Khloé take a weekend trip to Santa Barbara, California to have one final trip before the baby arrives, but Kim and Khloé leave Kourtney out of everything and get drunk, upsetting Kourtney, who must abstain from alcohol. Meanwhile, Kendall signs a modeling contract and Kylie gets jealous.

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.

Khloé makes a "love tape" for husband Lamar Odom while he's on the road, but it's extremely non-sexy; Scott and Rob watch it with Lamar, who thinks it's a joke. Kourtney misses intimacy with Scott, but is afraid to have sex because she doesn't want to hurt the baby. She later takes a Sex During Pregnancy class with Scott, and begins to enjoy sex again.

Khloé gets excited when she thinks she's pregnant, but it turns out that she isn't. When Kim lies to everyone to get out of doing things, Kris and Bruce get upset, but she may learn a lesson when she lies to Kendall and Kylie.

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.

Khloé and Lamar Odom get married. Rob attempts to rekindle his relationship with his ex-girlfriend Adrienne Bailon. Kim realizes she misses her boyfriend Reggie Bush, and Kourtney and Scott try to improve their relationship.

Kourtney and Scott find themselves pitted against her family, especially Khloé, because they disapprove of him.

When Khloé slaps Scott, Kourtney won't talk to her until she takes an anger-management class. A friend gives Kris a male-enhancement drug and she tries it on Bruce by slipping it into his coffee but Rob accidentally gets that coffee cup and almost lands in the hospital because of what follows.

Bruce goes to a charity event for the Boys & Girls Clubs of America. Kourtney, Kim, and Khloé were set to attend, but to his disappointment, they don't show. He decides to hold a charity boxing event for the American Heart Association and the people they fight turn out to be harmful for them. When Kourtney babysits for a friend, she realizes she isn't prepared to have her own baby.

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.