This Is Us writer breaks down Kevin's triple-romance mystery — and explains Miguel's health

Warning: This story contains spoilers for Tuesday's episode of This Is Us, titled "The Day of the Wedding."

Now that you've spent years getting used to Kate and Philip's relationship — or at least one week — This Is Us cordially invited you to the couple's nuptials in wine country on Tuesday night. The cabs were flowing, as were the mimosas, but the marriage merriment was mixed with melancholy and mystery.

Welcoming viewers five years into the future, "The Day of the Wedding" showed the celebratory ceremony for Kate (Chrissy Metz) and Phillip (Chris Geere) and showcased the debilitating effects of Alzheimer's not just on Rebecca (Mandy Moore), but her family as well. Concerns were raised when Rebecca conversed with her son Kevin (Justin Hartley) as if he were her late husband, Jack (Milo Ventimiglia), and it wasn't clear until the last second if she'd be able to sing and play piano at the wedding. (Hushed whispers gave way teary applause.) Meanwhile, Rebecca's husband/family glue Miguel (Jon Huertas) struggled to keep it together when clinking glasses with Randall (Sterling K. Brown) given the stress of managing Rebecca's care and... possibly his own? (His hand tremors were just a side effect of his blood-pressure medication, he assured Randall.)

To accompany the sentimental and the sad in this episode, though, was some silly. Beth (Susan Kelechi Watson) and Madison (Caitlin Thompson) teamed up as romance detectives to try to crack the case of whom Kevin had spent the night with; as they processed suspects and clues (a love letter/poem/lyric sheet? a bra? a floral wrap?), their snap judgments turned on a dime. The episode ended on a sleepover cliffhanger: Did Kevin spend the night the wedding singer named Arielle (Katie Lowes), friend-formerly-with-benefits Cassidy (Jennifer Morrison), or always-on-again-off-again ex-wife Sophie (Alexandra Breckenridge)?

Let's don a kilt, be equal parts sexy and depressing, try to look government-issue handsome, detect notes of tobacco and cherry cola, and get our Agatha Christie on with executive story editor Jon Dorsey, who wrote "The Day of the Wedding."

ENTERTAINMENT WEEKLY: This Is Us has been down this wedding aisle with Kate before, so to speak. But instead of spending lots of time with Kate and Phillip, this episode delves into Rebecca's deteriorating condition and the toll it's taking on Miguel, and it revels in a different kind of mystery for the show — a comedic one — about Kevin's romantic activities the night before. How did the writers go about brainstorming and plotting this episode?

JON DORSEY: Naturally, as we're starting to get towards the end of the series, there's a bittersweet kind of element. There's a sadness to it coming to an end. So we wanted to find a space to have a little bit more levity — and this gave us an opportunity to do that. I was really happy for that, so we're not just stuck in the sad space. And it was a great opportunity to play with Kevin since we're jumping forward five years and sitting in that era as our primary time period for the first time. Fans aren't going to really know what necessarily happened with all these characters over those five years.

The previous episode is pretty much dedicated to Kate and Phillip's story. So we get a little bit of that. And like you said, we've already done the Kate wedding. So we didn't want to live in the ceremony too much. We wanted to see, "What are some cool stories that can tell around that with these characters that we haven't seen before?" You could tell that when we actually get to the formal ceremony, we're moving through it pretty fast. Been there, done that. But it's all this swirling interesting stuff that's happening around that — especially with that five-year jump. What's happening with everyone? Where have we dumped them by jumping forward in this time period? What's the fun stuff we can have with that as well as progressing Rebecca's illness? There's a natural built-in arc that we're going on with Rebecca and her illness. All that is sad, but it's organic to life and to the show.

Executive producer Elizabeth Berger said last week that there is still a final chapter to be told between Kevin and Sophie. The audience knows that Sophie was engaged to a man named Grant, and later, when she called Kevin to congratulate him on his wedding, she said that she had changed her number and it was "a long story." That scene didn't show her ring finger. When Sophie was reintroduced in last week's episode, viewers were told that she was married. Is that to Grant?

Yes. That is the same guy she's married to.

Do viewers get the "long story" in this next episode?

I'll say this. If you don't get it in the next episode, you'll certainly get it by the end of this season.

Kevin's "Mawidge" speech is a Princess Bride reference, which is a movie that was special to Sophie and Kevin. Just a small coincidence or a thing that might make viewers go, "hmmm..."?

Well, to be honest, it might be a little bit of both. When people come into your lives, especially when they're important people, that sticks, and it helps develop who you are as a person. So whether they stay in your life or not, they still help mold who you are. So Kevin's experience with Sophie, even when he was in his twenties when they were married, and they were such huge fans of The Princess Bride — that helped mold him. So even if they aren't together in the present day timeline, he's still a fan of that movie. So, in the back of his head, maybe subconsciously, there was something about Sophie that inspired him to give that speech. But also it's just him being typical, funny, self-deprecating Kevin, who was just always a fan of that film.

What can you say about Cassidy's mental health after her crisis? She seems healthier.

She is in a great frame of mind. She's mentally healthy, physically healthy — just in a great state in her life. I don't think that we will be touching on the specifics of how she got to that place deliberately or explicitly, but I think it's safe to say that she is continuing to get the help that she needs to be her best self. And when we find her in this five-year jump, she is certainly in that best-self space.

The episode leaves viewers on a Kevin cliffhanger with three possible options: The wedding singer; Cassidy, who was seen going into his hotel room; and Sophie, who is married but came solo and seemed to be having relationship issues in the past. It wouldn't seem like a huge payoff if it turns out to be the wedding singer in terms of emotional stakes, but what cryptic hints can you provide about the mystery resolution?

Kevin has had a lot of interesting love interests throughout the show's life. Sophie is certainly one of them, Cassidy is certainly one of them. And we're introducing a new potential love interest in this wedding singer, Arielle, who is a friend of Phillip. What I can say is they are all potential suitors. Obviously fans will understand why in terms of Sophie and Cassidy — and hopefully they'll understand why Arielle is a potential suitor who could be perfect for Kevin as well [once] they've watched these two episodes…. I would say: With This Is Us, always expect the unexpected.

So, don't count out the wedding singer?

Don't count out anybody. One of the beautiful things about This Is Us, which is also one of the cool things, is this time jumping, which allows to build up a connection between characters very quickly by establishing a long longevity of relationship within a short period of television time. So I think that that's a potential cheat code that could overcome some of the obstacles that you might be suggesting. But that's not to say that that is what we're going to do. But it could be.

Okay, is this something that you can say definitively: Is this person the end game for Kevin? Will he finally figure it out — no more corporate spokespeople?

Knowing that the show is so close to the end, I would suggest that this is more or less going to be an end game for Kevin romantically. But again, there's still five episodes left. So expect the unexpected. [Laughs]

Should viewers go back and study the scene in Kevin's hotel room from the season 5 finale?

I mean, we certainly did in the writers' room, so absolutely feel free.

Did the writers already have the plan in place for the answer to the mystery back then, or did you reverse-engineer the clue?

Like all great television, it's a little bit of both.

The episode pairs Beth and Madison as quippy romance detectives, and they have the best lines of the night. But was it a little bittersweet to discover this combination so late in the show's run, like, "Oh, we could have done so much with this?"

I'm not going to lie: Hell yes! [Laughs] They were so good together. I had so much fun writing their scenes. Everyone in the room had so much fun envisioning their scenes. And then when we were on set, Susan and Cait were just so good with their improvisation and understanding the timing of the jokes and just putting their own spin and funk on everything. There are so many [great lines] on the editing room floor that just couldn't make it, because of time. But frankly, I could have written a whole episode with just the two of them. And shoot, that could be the spinoff, you know? I would watch a series of the two of them being romantic detectives. It was that fun.

The last time Kate got married, she dreamed that Jack was alive and still married to Rebecca. This time, Jack returns in the mind of Rebecca, who's battling Alzheimer's. We've seen Jack woven into present day a few times before, but what was the challenge in creating this one? It was maybe the saddest one.

[Dr. Freddi Segal-Gidan, who has served with Dr. Michael Rafii as one of the show's consultants on the Alzheimer's story line] cleared all of these scenes for this episode specifically. In talking with her, she always spoke about how we can't try to be logical about the disease, because sometimes we don't really know what's going on in someone's head when they're dealing with this — especially at the stage that we are at with Rebecca. Sometimes they can flow in and out of being lost in time, or who they're even speaking with.

On the surface, we just thought it was a cool emotional way to depict that. I have to give a lot of credit to our director, James Tekata, for coming up with that beautiful in-camera reveal that she was seeing Kevin as Jack. But in reality, I'm not sure we know how someone's brain is working, whether she would literally see Jack walking in instead of Kevin. We're that lost in terms of the logic of the disease. But the doctor made it sound like this happens. This is a natural thing to ebb in and out and mistake who you're talking to and living in a completely different time period. It's sad, but it's real. A lot of the writers — especially the writers who have parents who've dealt with it — they were big on making sure we don't play it safe. Let's not be scared of presenting it the way it is. The doctor called it a family disease; oftentimes the person who's dealing with it isn't necessarily aware that they're dealing with it. It's all the family members around them who are aware and have to adjust. That's what we wanted to show in this episode.

Milo has talked about how he always wishes that he could have more scenes with the present-day Pearsons. Was he excited to get another shot?

I believe so. It was such a short, simple scene for him, even though it carries so much weight in the episode. It was interesting. And he's such a professional. You could tell that he had studied Justin Hartley, so that he could embody him in that scene. It felt like a different version of Jack, which is so cool — and nuanced to nail that. I was very happy with that scene.

Miguel knows on an intellectual level what's happening when Rebecca believes she's talking to Jack, but what do you think is going on his head? He's lived in the shadow of Jack for many years, and now Rebecca is having conversations with Jack.

I can't speak for everyone, but that's one of the saddest collateral of all of it. It feels like Miguel is cast aside at times, like the second fiddle. But it's not necessarily true. People can have multiple soulmates. And there's an argument that that's the case here. Another thing that the doctor was mentioning is, just because Rebecca might be in a period of thinking she's talking to Jack, it doesn't mean that she can't still be loving Miguel in that moment, if that makes any sense. It's this weird swirl.

I'm sure that Miguel knows that by talking to Rebecca's doctors. He's a smart person who is able to accept that and embrace it. But also, it is exhausting. And that's part of his story arc in this episode. He's such a good man that he's suppressing some of these natural frustrations that anyone would have, but there's an opportunity for him to let it all out to Randall. And we all would be lucky enough to have someone that we can just vent to sometimes, especially when stuff just is feeling really hard or life is feeling like it's moving too fast. And I think that's what he is touching on in this episode a little bit. It's sad, but I'm sure he's able to find a place where he realizes she's capable of having love for her past husband and her current, all at once.

This episode shows again how valuable Miguel is to this family and how he's been their strong, silent, secret glue. But we also see that he's on blood pressure medication and his hands are trembling, which he says is a side effect to the medication. Is he hiding a bigger condition such as a tumor or Parkinson's — which would be a lot, considering Rebecca is battling Alzheimer's? Are you possibly setting up the explanation for his absence at Rebecca's deathbed?

I'll say that we're not really setting up some kind of major disease. I think you've hit the nail on the head; it'd be a little too much, a little hat-on-hat kind vibe. I would probably take his word for it in the episode. He says that the trembling is just a natural reaction to that stuff. It shouldn't be worrisome. It's just, you know, people getting old. When you get to a certain age, sometimes you shake a little bit and it's not anything to necessarily be worrisome. Surely it could be a sign of something else, but that's not what we're going for here. In this episode, he's fine. He's just aging, and with age comes deterioration.

The wedding sequence culminates with Rebecca playing and singing an original song that features motifs from the show's theme music. ["The Forever Now" is written by This Is Us composer Siddhartha Khosla and Moore's husband, Taylor Goldsmith.] It's an emotional performance and all of the Pearsons are tearing up while watching Rebecca perform beautifully. Were there extra emotions flowing in the filming of that scene because it felt like the beginning of the end of the show? Or was it just, you know, good acting?

Probably a little bit of both. But I'll tell you: On the set that day, Mandy actually performed that live on set, and she was incredible. I think that most of the cast and crew hadn't heard any of the song before. So I want to say that a lot of those reactions were at least partially genuine.It went dead silent. I mean, even the crew members — you know, a lot of 'em are rough-and-tough kind of dudes; I saw them wiping some tears away. So I think a lot of that was genuine. Not only because the song was just beautiful and her performance was beautiful, but because it kind of signified a little bit of the beginning of the end of the series.

But was the most important moment of the episode actually the origin story of Jack's mustache in the '80s flashback scenes?

A hundred percent!

Do you remember where that idea came from? Is that something the writers have joked about over the years?

We've joked about it a little bit over the years. I think my first or second episode when I was on set, I was talking to Milo about his mustache. I think he grew out a real one for his audition for This Is Us, and he was just so proud of being able to grow that thick, real mustache. So I always remembered that. And then it came up naturally for this episode in the room; I forget who pitched it. We get three versions of Jack's facial hair in this episode: We get to see his full beard, we get to see the porn 'stache, and we get to see the goatee in that vision. So that was kind of fun and cool.

It all just kind of fell into place. When we have this stuff in our back pocket, we're always wondering, "Oh, that'd be cool, but does it make sense in terms of our linear storytelling?" So we have to dissect everything. Because in this [flashback], we're living in around 1986, so it's like, "Okay, is it possible that Jack could have had a mustache in '86?" And then after we do all of that, we're like, "Yes, he could! Let's do it!"

Next week returns viewers to the wedding — as well as the night before. What's a final hint that you can drop?

Whenever you have a big enough fanbase as we're lucky to have, when certain kind of arcs, especially romantically, maybe come to an end... I'll say this: Some people will be happy and some people might not be happy. We'll see.

This interview has been edited and condensed for length and clarity.

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