Despite Lena and Martin getting along as co-parents, they must determine the best way to orchestrate Milo's upcoming birthday festivities based on their new system of boundaries. Meanwhile, Oliver is pleasantly surprised when Jenna shares a birthday invite with an unforeseen guest. Elsewhere, Maya takes matters into her own hands and reveals a surprise guest of her own.

Frazzled by her intimate dream about Martin, Lena accidentally injures her tooth and reluctantly goes to the dentist; Martin escorts Lena to Mae's parent-teacher conference after she inadvertently gets high; Maya asks a familiar face out on a date.

Lena and Martin choose to share the house for the summer while the children are away at camp despite Lena's reservations, but soon realize it might not be the worst idea. They collectively agree to throw their annual backyard pina colada party where they will celebrate their independence from their children. Elsewhere, a friendly face returns back home and Martin can't help but see it as

Vlad announces that construction on the house is almost finished; Martin begins dating a divorcee who works in his building; Camille tries to be a good influence on Arthur's nephew.

After a doctor's visit, Arthur learns he's under stress due to the approach of Valentine's Day; Arthur asks Camille if they can take a break from the holiday; Lena decides she wants to cook a platonic Valentine's Day dinner for Martin.

Martin and Lena are thrilled when they hear that Mae has won the lead in the school musical but are surprised to learn that she has been confiding in the school psychiatrist, Dr. Rydacto, about her feelings toward how not divorced they are acting. Meanwhile, Martin has reservations about how fast his relationship with his girlfriend is going and asks Mason for girl advice.

Lena confirms that she has feelings for Martin but is confused when his response is not what she expects. To escape the situation, Lena joins Camille and Maya on a road trip for a girl's weekend before Maya's baby arrives. Meanwhile, Martin, still considering how to respond to Lena, joins Arthur, Frank and Henry in chasing after the women.

Lisa's unexpected pregnancy causes more complications than what Lena and Martin anticipated. Without Martin's knowledge, Lena decides to help Lisa despite her insistence about not wanting them involved in the baby's life. Meanwhile, Mae and Mason try to force Lena to admit that she and Martin are back together. After Maya's false labor scare, she returns from the hospital and is put on bedrest by Frank who insists on taking care of her.

In an effort to connect with their kids and bring the family closer together, Lena and Martin plan a fun outing, only to be interrupted by a blackout. Elsewhere, Lena urges an overdue Maya to get induced but must succumb and honor her birthing plan. Meanwhile, Martin continues to try and figure out where his relationship with Lisa stands.

With this being Martin's week in the house to take care of the kids, he discovers that daughter Mae finds his parenting skills to be lacking and a bit sexist. Meanwhile, Lena's time in the garage gives her time to contemplate going out with a handsome doctor and perhaps taking the relationship to the next level.

Lena goes out on another date with Wes, whom she's smitten with; but unbeknownst to her, Martin is doing his best to take care of a sick Milo. Meanwhile, Maya makes a decision on whether or not to become a single mother.

Lena tries to support Maya with her pregnancy, only to get accused of being too controlling; after Martin reads Mae's diary, he suspects that she is romantically involved with her teacher and panics.

Unbeknownst to Lena and to her dismay, Martin starts to date a familiar face and surprisingly begins to see the world of relationships through brand-new eyes. Meanwhile, Lena tries to show she's a good role model to her kids by proving a point and faking a night out on the town.

Martin grows suspicious of Lena's strange behavior when she begins sneaking out of the house to secretly help Lisa Apple with her baby. Lena tries to avoid Martin but feels she needs to tell him the truth about her arrangement with Lisa. Meanwhile, Martin takes Mae on a driving lesson, which turns into a hot pursuit.

While Lena gets ready to go out on a first date with a handsome man whose sexual chemistry is undeniable, Martin finishes his dance lessons with Charlotte and attempts to try to fix things with Lena on what would have been their 16th wedding anniversary. Meanwhile, Mason is being teased by his friends for not being as sexually active as they claim to be; and to prove that she would be a good mom, Maya attempts to watch over Lena and Martin's kids, with questionable results.

After Lena and Martin sleep together, Lena searches for signs that they are or aren't meant to be a couple; Arthur and Camille trail Lisa Apple, hoping to determine if she is pregnant with Martin's baby.

Things get complicated after Lena and Vlad kiss; Martin goes to Paige's house for more privacy but feels uneasy; Mae finds out that Mason has a crush on a girl at school.

Lena and Martin announce to the kids that Lisa Apple's baby, Annie, is their half-sister, and Martin is surprised when they aren't interested in meeting her. Lena feels the burden of being stuck in the middle between Martin and Lisa but still offers to help bring both families together. Meanwhile, Mason overhears Lena and Martin's conversation about Lisa's financial difficulties and decides to start a fundraising campaign to help. Elsewhere, Lena feels a bit of empty nest syndrome.

Martin finds every way he can to avoid asking Lisa Apple if she is pregnant; Lena worries Mason is changing himself to please his new girlfriend; Maya tells Frank a made-up story about a friend who is dating someone new.

Camille urges Lena to become more active on social media to get her business off the ground; Martin takes over for Lena as Milo's room parent and investigates why Milo is feared by his classmates.

Lena and Martin battle for control of the house; Milo announces he wants to go to a school for the gifted; Lena and Martin give conflicting advice to Mason on how to deal with his recent breakup.

After breaking the news to friends and family about the divorce, Lena has to deal with her son Mason's growing pains; Martin secretly tries to atone for an oversight and surprise his ex-wife.

Lena decides to call Martin's bluff on selling the house but is surprised when he begins getting the house ready for sale; Lena tries to cheer up Mae by inviting her friend from camp to visit; the friend seemingly brings supernatural events with her.

Lena and Martin have opposing mind-sets over the new contractor's repair methods; Martin takes Mason camping to help him get over his breakup with Hazel and to teach him how to be a man, but learns from him that it is okay to express his emotions.

Milo complains that Grandparents Day is coming up at school and doesn't feel Henry is interesting enough to participate. Lena and the kids urge Martin to reconnect with his long-estranged father, Brock, to rebuild their relationship. Meanwhile, Lisa continues to struggle financially and considers moving back home with her parents. Elsewhere, after listening to a true crime podcast, Maya worries that Frank has a dark past he has been hiding.