In the season 12 opener, old feuds are still hot topics among Vicki, Kelly, Shannon and Tamra, with battle lines clearly drawn in the sand. While awaiting apologies that aren't forthcoming, Vicki is busy expanding her business and moving offices, Tamra is reuniting with an old friend who shares her faith, while Shannon struggles with her weight and her marriage. Kelly's concerned her mother's becoming a hermit and Meghan is making her way back to Orange County after the birth of her baby, Aspen. Returning housewife Lydia, now a mother of three, is determined to bring Tamra and Vicki back together but soon realizes she may be in way over her head.

Vicki prepares for her big office move while Shannon enlists the help of her feng shui expert to try and bring balance into her otherwise chaotic life. Lydia is busy launching her brand new magazine which features Peggy, an Armenian firecracker, whose life may look perfect but not everything that glitters is gold. Kelly struggles to make her marriage work while Meghan settles into life as a new mom. Tamra plans an over-the-top birthday party for her granddaughter, Ava, where tempers fly as Lydia and Shannon meet for the first time and don't see eye to eye when it comes to Vicki.

Trust issues plague Vicki as she organizes her new office. Also, Peggy deals with her looming surgery; Tamra is thrust back into a past role; and Shannon confronts her weight gain as well as her nemesis, Kelly Dodd, who crashes dinner.

While the fallout from The Quiet Woman leaves Shannon and Kelly both stunned, the ladies move on with their lives as Shannon takes her daughter Sophie out for a driving lesson and Kelly looks to improve her love life from the inside out with vaginal rejuvenation. Lydia’s mom, Judy throws a birthday party from her grandson Stirling, where Vicki forms an instant bond with new housewife Peggy. Tamra looks to break the cycle of parental alienation and divorce in her family.

Tamra and Shannon have their first face-to-face with Meghan's new baby and learn they'll soon have to face Vicki. Lydia's family takes a luxurious Hawaiian vacation full of uncomfortable conversations, while Kelly tackles her fears about her mother's mortality and her desire to move on with Tamra and Shannon. Vicki tries to settle into her new office and meddle in her son's love life while Peggy invites her friends to the unveiling of her custom-designed Lamborghini.

Vicki tries to balance her life alongside her relationship with Steve; Lydia plans a launch party for her new magazine; Tamra organizes a sit down for Kelly and Shannon; Megan hosts a Sip-N-See for baby Aspen.

Lydia is hopeful everyone can get along for her magazine's launch party; Tamra struggles with the scars of her broken family; Tamra thinks Peggy is overstepping her bounds, and things end up not so noble at the Nobleman launch party.

Vicki turns green with envy after learning that Kelly is celebrating St. Patrick's Day with Shannon and Meghan; Lydia wonders if her son's prophecy will come true as she competes in a race; Meghan, Shannon and Kelly indulge in whiskey and whimsy.

Kelly suspects her new pal Shannon of being up to her old tricks and confides in Meghan. Meghan puts her detective hat back on to investigate Vicki's issues with Shannon and Tamra. Vicki's looking to move forward with her new love, while Peggy takes her daughter to New York. The ladies attend a Drag Bingo event, where Lydia faces a moral dilemma and old arguments spark anew.

Meghan is still reeling from Kelly’s attack at Drag King Bingo. Lydia tries to play mediator but is unable to stay impartial. Tamra gets an unexpected phone call that leaves her wondering if there is still hope for her and Vicki. Peggy prepares to send her daughters off to college. Shannon celebrates her birthday but is faced with the harsh reality that this year there will definitely not be a renewing of her and David's vows. Vicki throws a blowout party for her birthday and an old friend reveals some juicy details about Eddie’s past.

As rumors swirl around Orange County following Vicki’s birthday party, Tamra catches wind of what transpired about Eddie and is livid. The "Friendship Whisperer" Lydia is even perplexed by Vicki’s motives and is nervous for all the women to converge at Kelly’s beach volleyball party. Kelly is having a breast reduction and decides to have a "Boobs Voyage Party" with all the women except her former bestie, Meghan. All hell breaks loose at Kelly’s party when Tamra and Vicki finally talk face-to-face.

Kelly undergoes surgery with the support of her husband; Tamra shares her concern over Shannon's behavior; Vicki and Shannon visit Kelly while she recovers; Peggy fends off digs from Kelly; Lydia discovers Shannon failed to invite her to dinner.

Lydia throws Doug a party aboard a yacht to say farewell to his fertility and invites all the ladies despite her hurt feelings over being left out of Shannon's dinner. At the party, Peggy is infuriated when David questions Diko about her health. Meanwhile, Easter arrives in the OC and Shannon looks to her mom for advice about her marriage with David. Meanwhile, Vicki decides to call Tamra to finally meet and end their feud once and for all.

Vicki and Tamra finally come face-to-face to see if there is any hope of redeeming their broken friendship. Lydia discovers the joys of when the rich get richer. Kelly's dad comes to town and she discovers the parallels between her parent's dysfunctional relationship and her own. Peggy and Diko celebrate their 22nd wedding anniversary with the ultimate Armenian inspired party while Shannon faces the consequences of her prying husband's actions.

While Vicki visits her cardiologist to check up on her broken heart, Shanon and Peggy are still simmering about the cancer questioning that took place with their husbands. Lydia and Doug plan a Nobleman Iceland trip and Doug encourages Lydia to invite her friends at Meghan’s dinner party with her psychic. All hell breaks loose when Peggy confronts Shannon about David grilling Diko about her cancer. As everyone gets ready for their big trip to Iceland, Shannon wakes up regretful for how unraveled she became with Peggy and confesses to Tamra about the current state of her marriage.

The ladies of Orange County are ready to explore everything in Iceland from hiking a glacier to sampling the exotic cuisine. While Tamra and Vicki seem to be reconnecting, Lydia and Tamra hit a bump in their friendship. After a long day of activities the ladies are faced with a shocking medical emergency.

Vicki's health scare continues and brings out a side of Peggy that shocks the ladies. Later, a broken friendship might finally be on the path to mending, while a drunken night causes fractures in another.

After being hurt by Kelly's words, Peggy reveals a secret video to Lydia. Meanwhile, the rest of the ladies whoop it up at a Viking dinner where Tamra and Vicki continue to get along, much to the dismay of Shannon. When Peggy finally arrives at the dinner, her preemptive strike on Meghan thoroughly backfires. Once everyone returns to the OC, Shannon discovers the nature of her unbalanced behavior, but also finds her marriage on thin ice.

Vicki surprises her son Michael with a new role at Coto Financial, while Kelly complains to her mother that she's finally at a breaking point in her marriage. Tamra fulfills her greatest wish of attending her estranged daughter's high school graduation. The ladies celebrate the launch of Meghan's new candle line and Peggy finally comes face-to-face with all the women after her sudden departure in Iceland.

The ladies reunite to discuss the events of the 12th season with Lydia being questioned on her opinions. Vicki reports on the latest developments in her relationship with Steve, and Kelly and Shannon both dissect the state of their marriages.

The second part of the reunion gets underway with Kelly and Meghan getting into their series-long feud. Peggy lists her complaints to Shannon, and events take an unexpected turn, leaving the housewives reeling.