The ladies kick off an explosive 11th season with an epic boat party filled with tensions at an all-time high as Vicki fights to win the ladies back after a year of lies left her friendless and alone. Heather's mansion is still a work in progress, and so is her relationship with her workaholic husband Terry. Shannon's marriage is on more solid footing, so it's time to look for a new home for her family. Unable to have children the old fashioned way, Meghan starts in vitro fertilization (IVF) with no help from husband Jimmy. And new housewife Kelly Dodd brings her big personality to the party, but her loud mouth gets her in big trouble.

While Heather travels to Turks and Caicos to help Terry reconnect with their kids, Tamra tries to save Ryan and Sarah's relationship. Meanwhile, Kelly decides to befriend Vicki against Meghan's warnings. As Shannon continues to rebuild her relationship with David, Vicki does the same with her business. Later, Meghan invites the ladies over to her new house to demolish her kitchen; however it's Kelly who seems to smash her chances of friendship with the girls when she reveals she has befriended Vicki.

Vicki and Briana take a road trip from Oklahoma to Orange County when Vicki finally gets her wish, her daughter is moving back.  But Briana's homecoming is not all that Vicki hoped. Meghan faces her fear of needles head-on when she begins her IVF shots without Jimmy, as Heather struggles with her children's expectations about how much they see their father. Kelly throws a beach party to get to know all the women better and Vicki and Tamra pull their heads out of the sand to try and resolve the issues that have plagued them for the past year.

As Kelly's beach party moves indoors, Vicki and Shannon have a chilly face-off about the fate of their friendship. Meghan meets Jimmy's frozen sperm for the first time as the couple moves one step closer to starting their family. Heather laments how Terry's tough schedule is jeopardizing their family unit and Meghan advises Kelly to keep quiet when it comes to her opinions on Vicki. A medical emergency lands Briana in the hospital, leaving Vicki to step in as single grandma. Shannon enlists Tamra's help in making a tough decision regarding Vicki.

At Shannon's 70's-themed party, disco fever takes on a whole new meaning when Shannon gets into a heated argument with Kelly about her rumor-filled past. While Vicki juggles work, babysitting her grandsons and nursing Briana back to health, she still finds time to "whoop it up" with the ladies, at least the ones who are speaking to her. Heather confronts Terry about his lazy parenting after he schedules a work trip for Mother's Day. With Jimmy out-of-town again, Meghan looks for support from her friends during her IVF treatments. Tamra tries to help Kelly mend fences, but winds up stirring the pot instead.

In the wake of all hell breaking loose at Shannon's 70's party, Shannon heads to Dr. Moon to try a new remedy to remove toxins. Kelly tries to make amends by inviting Shannon to sit down and rehash the night. Meanwhile, Meghan travels to Washington, D.C., with Heather by her side, to speak on behalf of colorectal cancer. Tamra explores custom bikinis for her fitness competition and Vicki tours Briana's new house in the midst of renovations.

While Vicki revels in the return of her family to Orange County, Heather strives to find a work/life balance on the eve of her book launch. Kelly struggles to figure out Shannon's motive for setting her up and bonds with Vicki over their shared anger. Tamra plans a last hurrah for Meghan before she gets pregnant, but the sushi party goes off the rails when Kelly loses her cool and crosses a line.

After an explosive night at the sushi dinner, Heather and Tamra discuss Kelly's volatile behavior as Kelly regretfully turns to her friend Meghan and receives some tough love. Meanwhile, Meghan takes the next crucial step in her IVF process. Later, Shannon celebrates a night full of surprises with all her friends and family. Back in the OC, Vicki and Kelly have a party of their own and bond over being the odd women out.

While Shannon heads to Cabo with David, Tamra and Kelly join Vicki at the luxurious Merv Griffin estate in La Quinta, California to celebrate Vicki and Briana's upcoming birthdays. Heather and Terry enjoy a date night dinner where they discuss his busy schedule and her problems with Kelly. Later, Tamra arranges a meeting between Kelly and Heather to work out their differences before the ladies head to Glamis.

Tamra, Vicki, Heather and Kelly travel to Glamis to celebrate Eddie's birthday. While the trip is supposed to be down and dirty fun, Tamra and Heather are still wary of Kelly's filthy mouth. After a long RV ride down, the ladies finally get some fresh air and see what the motor sports mecca has to offer. The next day, the ladies set out to explore the dunes, leading to a ride they will never forget. Meanwhile back in Orange County, lives are forever changed as Meghan receives the results from her pregnancy test and Shannon's holistic home has finally sold, leaving the Beador's two weeks to move out.

As the women recover from the accident in Glamis, Tamra returns intent on carrying on with the trip. New alliances form in the wake of Meghan and Shannon's refusal to visit Vicki at the hospital. Back in the OC, Tamra contemplates postponing her fitness competition. While Meghan goes to Vicki's house to make amends, Shannon attempts to get back into her friends' good graces.

Shannon panics about her families' impending move, while her daughters prepare for an upcoming rock show. Vicki celebrates Briana's birthday and makes it uncomfortably clear she is ready to fill up her love tank. The ladies come over to help Shannon purge her outdated closet; however tensions run high over unresolved issues between Shannon and Kelly, as well as Tamra and Meghan. Friends and family gather to watch the Beador girls perform, but Shannon's night is rocked by a shocking allegation from an uninvited guest.

Michael and Kelly discuss the ups and downs of their relationship since separating, while Meghan goes to her first ultrasound appointment. Vicki gets asked to film a commercial for a cancer charity. Shannon packs up her old home and gives it a heartfelt "goodbye" while Tamra hosts Kelly, Vicki, and Heather for a day of pampering and luxury at Glen Ivy Spa. Unfortunately, things at the spa aren't as tranquil as expected when Kelly tearfully opens up about her rocky marriage.

Meghan throws a party to celebrate the grand opening of her candle store. Tensions ignite as Vicki threatens to expose a secret about Shannon that leaves all the ladies confused. As Kelly and Michael try to navigate their tumultuous marriage, Meghan and Jimmy try to get a handle on her highs and lows of pregnancy. Meanwhile, Heather throws a fancy party filled with mixed emotions and cocktails to celebrate the release of her book; where Vicki and Shannon finally confront one another and Meghan proposes a trip to Ireland to investigate her heritage.

The ladies jet off to Ireland to explore Meghan's heritage and try their luck of the Irish. On a pub crawl, an over indulgence of spirits leads to a sobering exchange of words between Tamra and Kelly, ultimately pushing Tamra over the edge. With Kelly on the outs, the rest of the ladies try to salvage their first day in Ireland by enjoying a traditional Irish Hooley Night.

After a bumpy start to their vacation in Ireland, the women head off on separate adventures. Meghan takes Kelly to nearby Greystones Village in an attempt to locate distant relatives, while Vicki, Tamra, Heather and Shannon travel to a milk farm to get up close and personal with Ireland's finest cows. The two groups reconvene for dinner where Kelly awkwardly tries to make amends with Tamra. However, the peace treaty doesn't last long, as tensions reemerge and bombs fly when the ladies make their way back to the airport, leaving this group of friends in disarray like never before.

The Ireland trip ends with the conclusion of the bus ride from hell. Back in Orange County, the women try to make sense of their war on foreign soil, while Meghan escapes to St. Louis to get away from the drama. After months of strict diet and exercise, Tamra is finally ready to flaunt her body on stage at her long awaited fitness competition and the ladies gather to cheer her on.

In the season finale, the ladies gather together at Shannon's new house for a carb-loaded affair to celebrate Tamra's victory at the fitness competition. However, with the residual anger surrounding Vicki's loose-lipped gossip, Tamra, Heather and Shannon decide it's time to shut down the rumor mill. After an evening of avoidance, they finally confront Vicki about her vicious rumors.

The reunion kicks off as the women come together to grill Vicki on her journey from outsider, to insider, to outsider again. Tamra talks religion, being a peace maker and her award-winning a* while Meghan opens up about her baby blues and her relationship with Jimmy. When the '70' party accusations fly, new housewife Kelly stands her ground.

Kelly faces the music for her behavior this season and reveals some shocking secrets about her past. Heather goes head-to-head with Kelly about her outbursts at the sushi party, while Shannon talks about her vow renewal and rocky relationship with her mother-in-law. Vicki’s daughter Briana visits the couch to dish about her mom's relationship with the truth.

The reunion concludes with the ladies recounting their traumatic experience in Glamis. Old wounds are opened as Meghan finds herself on the defensive for her lack of sympathy towards Vicki after the accident. When the ugly drama of Ireland is discussed, emotions run high and Shannon is driven to her breaking point.