This post contains spoilers for Season 4, Episode 18 of “This Is Us.”

If the Season 4 finale of “This Is Us” had an unofficial theme, it would be doctors giving really good advice and people actually taking it (how timely and relevant!). But that’s just the cream-filled center of this episode, which packs in its fair share of emotional whiplash as the show’s writers’ room continues its ongoing quest to remind us just how complicated and heartbreaking and beautiful life can be.

The episode finds the Pearson family gathering for Jack Damon’s first birthday. Kate and Toby, in a better place after a rocky few months, are overjoyed to celebrate their son’s hard-fought milestone. The baby looks like a true (and very adorable) Pearson in his head-to-toe Steelers gear. Kevin almost immediately offers Randall an olive branch following their tense exchanges about how to care for their mother in her early stages of Alzheimer’s disease.

Kevin, unaware that Randall guilted Rebecca into agreeing to do a clinical trial in St. Louis, tells his brother he knows his heart is in the right place. But, he says, the clinical trial is not what their mother wants.

In glimpses of the future, we see Jack Damon and his wife, Lucy, prepare to welcome their first child. (It’s a reminder that the episode is a callback to the season premiere, which introduced several new characters, including Deja’s boyfriend, Malik.) We also meet a couple new strangers who turn out to be integral to the Pearson family story: a gallery docent who may be dating someone very famous, and a man struggling to tame an unruly horse.

In the present timeline, Rebecca makes an impromptu announcement about her and Miguel’s impending move to Missouri. It doesn’t take long for Kevin to figure out what — or who — changed her mind. Randall doubles down on doing whatever he can to help Rebecca, whether she or his siblings are on board; Kevin insists Randall’s motives are selfish and that they should honor what Rebecca wants for herself.

The exchange turns really ugly. Kevin tells Randall he is trying to save Rebecca out of guilt for not saving their father. “If I had been there I would have walked through literal fire and I would have pulled that man out,” Kevin says. Randall reminds Kevin that he wasn’t there the night their father died, and suggests that Jack died “ashamed” of him. Then he insults Kevin’s acting. Kevin looks stunned before telling Randall that the worst day of his life wasn’t the day their father died. “Hand to God, Randall,” he says, “the worst thing that ever happened to me was the day they brought you home.”

Oof. Thankfully, this episode also features an appearance by Dr. K, the good-natured obstetrician who delivered Kevin, Kate and the sibling they would never meet. In flashbacks to the Big Three’s first birthday, Rebecca admits she’s struggling through her grief over the child she and Jack lost in the show’s first episode. Jack admits he still thinks about their other son, too. So, Rebecca and her husband do the sensible thing and visit the man who once told Jack that “there’s no lemon so sour that you can’t make something resembling lemonade.”

A modest Dr. K insists he can’t offer anything as great as his lemonade speech — in which he recalled how losing his first child made him want to go into obstetrics — before singing a few line of Irving Berlin’s widely covered “Blue Skies.” He tells Rebecca and Jack that this was the song he sang to his unborn child during his wife’s first pregnancy; it was also the song they listened to after they lost the baby. “It made us so sad. It was like we were punishing ourselves,” Dr. K tells the Pearsons. But then his wife got pregnant again, and Dr. K again sang “Blue Skies” to their unborn child. Twenty-five years later, he and his daughter danced to the song at her wedding.

“That song made us happy, it made us sad, made us happy again,” Dr. K says. “The whole human experience just wrapped up in that one song.” He reasons that hospitals — which see lives begin and end day in and day out — are also like that. But ultimately, he says, “life does have a way of shaking out to be more beautiful than tragic.” His wise words draw us back to what Jack and Rebecca’s musically inclined grandson is experiencing in the future: the gallery guide turns out to be the adopted daughter Kate and Toby decide they want after taking a photo of Jack to the newborn intensive-care unit, where he spent his first days. Though Kate and Toby’s future may be in question — sadly, we do not get a resolution to the couple’s fate in this episode — we at least know that Jack Damon has a sister.

The other very important stranger in this episode also happens to be a doctor, whose thoughtful advice brings us to the episode’s biggest bombshell: Madison is pregnant, following her and Kevin’s impulsive hookup a few episodes ago. Madison tells the doctor that she and the father barely know each other and she has no intention of telling him. “He comes from a long line of great love stories,” she says. “This isn’t what he wants.”

The doctor pauses for a moment, before telling Madison she should at least give him a chance to decide. And that’s how Madison arrives at Jack Damon’s birthday party with news that Kevin is the father of the twins (!) she is expecting. For Kevin — who has to deal with this life-changing news in the middle of his fight with Randall — it’s an unexpected path to the family he’s spent most of Season 4 dreaming about. He tells Madison he’s all in. We are all in, too, on seeing how these two attempt to co-parent — and how Kate reacts to her brother having a baby with her best friend.

This season has explored rifts within the Pearson family across generations — Jack and his estranged brother, Nicky; Kate and her mother; Randall and Kevin —— but in the end we see Kevin put his hand on his brother’s shoulder as they gather to say goodbye to their mother in a bittersweet glimpse of the future. We briefly saw Kevin’s son in last season’s finale; now we see that he has a daughter as well. Nicky is there to comfort the nephew who helped him turn his life around. Rebecca is seen in soft focus as old family photos play on a nearby projector.

The most unsettling part of this scene is that Kate is nowhere to be found. There’s one obvious (and heartbreaking) theory that could explain her absence, but the show offers no hints about her fate. Instead, “This Is Us” encourages us to appreciate the Pearson family lemonade and the lemons, however sour, that made it. Rebecca is beloved; she and Jack’s love will live on through their children and their children, and so on.

Even further into the future, Kate and Toby’s daughter wonders what her new niece’s name is. Jack Damon, zeroing in on the episode’s true theme, replies: “Hope.”

correction

A previous version of this post incorrectly referenced "Blue Skies" as a song by Willie Nelson. Though covered by Nelson and others, the song was written by composer Irving Berlin.

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