'This Is Us' : Jennifer Morrison Says There's More Cassidy in Season 6

This Is Us proved that finding love is not easy for most.

Tuesday's episode, titled "Heart and Soul" and directed by cast member Chris Sullivan, explored the relationships of many of the characters, including the mother-daughter bond between Rebecca (Mandy Moore) and Kate (Chrissy Metz); the crossroads for Deja (Lyric Ross) and Malik (Asante Blackk); as well as the return of Kevin's (Justin Hartley) friend and one-time hookup Cassidy (Jennifer Morrison).

The time-hopping series shared more backstory of Rebecca's life after the death of her husband Jack (Milo Ventimiglia), specifically her getting back out in the dating scene. Along with the support from Miguel (Jon Huertas), the Pearson matriarch went speed dating and was reintroduced to Matt (Matt Corboy) — the salesman and single father from season 3 whose kids attended middle school with the Big Three. Though Rebecca felt she was moving forward with her life, her date was the cause of a big blowup between her and teen daughter Kate (Hannah Zeile). Fast forward to the present day, Rebecca and Kate are now in a much better place in their relationship. While Rebecca, who is struggling with Alzheimer's, was told she could no longer babysit Kate's kids alone due to her latest PET scan, the pair found a new way of strengthening their bond by passing down a shared love for music and teaching Kate's son Jack how to play the piano.

Elsewhere, star-crossed lovers Deja and Malik break the news to Randall (Sterling K. Brown) and Beth (Susan Kelechi Watson) that they plan for Deja to finish high school early and move to Boston. With the possibility of their daughter moving six hours away and living with her boyfriend and his young daughter, Randall had a one-on-one conversation with Malik and suggested that he break up with Deja. The latest confrontation further added tension to Randall and Beth's relationship with Deja as they risk losing her by expressing disapproval of her choices.

Lastly, Kevin traveled across the country to check on the progress of his house, which he is building for Rebecca. The project is being overseen by Nicky (Griffin Dunne), who is happily dating his new girlfriend, stewardess Edie (Vanessa Bell Calloway). Not to be alone and a third wheel, the single Manny actor hit up the Pennsylvania-based Cassidy for company.

Below, Morrison opens up to PEOPLE about her "complicated and beautiful" character's relationship with Kevin and teases Cassidy's future with the Pearsons.

PEOPLE: When Kevin and Randall are on the phone, Randall jokingly calls his brother a "serial monogamous" and that the trip to the cabin is a "couples' retreat." When you read the script about this cabin trip for Cassidy, what was your reaction?

JENNIFER MORRISON: I loved the script and I can't say that is unusual with This Is Us. I'm always so excited to read the script because I feel like that's my chance to be the viewer that other viewers get to be when they watch the show. [laughs] I think it's so cool the way that they have woven Cassidy into Kevin's life, just because there's something really authentic about it. You feel like these are really two people that struggle. Their struggles are very different, but there is something in common in that struggle. They're very blunt and open with each other. And there's an intimacy that comes from that kind of honesty with a person, or I guess unfiltered honesty with a person. It's just interesting to get to read the other family members' reactions to Kevin even talking about being around her. Because obviously, that's not something Cassidy herself would know about. But for me, Jennifer the audience member, finds it highly satisfying to actually see other people weigh in with opinions about it.

Speaking of unfiltered honesty, is Cassidy the only one who can deliver the truth to Kevin when it comes to relationships? He's always been a hopeless romantic.

My perspective on it is just that there are certain people that come into our lives who activate us, and they are agents of change in our life. I feel like for some reason that unfiltered honesty makes Cassidy and Kevin able to be agents of change in each other's life. It's like they actually can trigger change for each other by being that way with each other. That's exciting to watch because obviously, the audience knows Kevin really well over a long period of time. He has gone in certain cycles over and over and over again. There's certain growth there, but then there are certain things that he keeps tripping over or getting stuck on.

For whatever reason, Cassidy seems to be someone who doesn't let him stay in that cycle when he's around her. She pushes him to be a little bit different — and maybe that's just because she does say the things that she says. Most girls are very taken by how handsome he is, how charming he is and how sensitive he can be. They let that be idealized in their minds when they come across him. Cassidy's just been through too much. She's a war veteran, and she's seen really difficult sides of life. She's a realist and she's practical. She's kind of immune to some of his charms. It's not that she doesn't see them, they're there, but she has a self-awareness to be able to call things for what they are. When she does that, it's disarming. Cassidy is just like, "Let's just call this what this is."

She told it to him straight and even called him a "big handsome wrecking ball."

The thing that I kept in mind, and I think the thing to keep in mind watching their relationship is, they — her and Kevin and Nicky — went to AA together a lot, which means they know each other's stories. They've heard a lot more of each other's stories than the audience has heard of each other's stories. Kevin knows some of the damage of what she went through, and he knows some of the terrible things that happened when she was having to negotiate things in really terrible situations overseas. ... So Kevin's very aware of how dark some of her life has been. I think that earns her that kind of honesty with him because she's not saying things to be mean, and she's not saying things to be flippant. She's just saying what she sees. She's just calling the truth as she sees it.

And she literally breaks down his failed relationship with Sophie and then, his failed relationship with Madison. Cassidy told him, "I'm too messed up already, leave me in peace." When she walked away at the end of their conversation over ice cream, was that her way of closing that chapter of their relationship?

The way I saw that moment was a way of Cassidy trying to protect how important Kevin is in her life. I think she knows that he's a good person and she knows that he does bring out good things in her, and she does truly appreciate their friendship and the connection that they have. She knows that his terms can be dangerous because it leads to an end, if it doesn't work out. She's not interested in there being an end, she's interested in there being a continuation. If that continuation means just being friends, she'd rather be friends than have an end.

So, there's certainly a little bit of just protecting her heart going on. But I think that as much as she calls him out and she puts him in his place, there's a part of her who's saying it because she's warning him that she could like him. She's not saying she does yet. She's just warning him that she is damaged, she is broken. She has these things that she has to work through, and she cannot just be another girl that he goes through and is done with and then still be okay. She's like, "Don't. Leave me intact. I get you. I understand you. I like you for you. And that's fine, but don't add to the damage that's in my life." I don't know that she is clear on what exactly that means at the end, but I think what she's clear on is that she doesn't want to not have him in her life.

How was working with Chris Sullivan as a director?

It was so wonderful to work with Chris Sullivan. It was so funny because it was meant to be … Well, I don't know if I'm allowed to say this or not. But originally, he was going to be on the show Dr. Death, which I directed. So, I was originally supposed to direct him. And then, because of the pandemic, everything got pushed and schedules changed. By the time it was going to happen, he ended up having to not do Dr. Death because of This Is Us starting up again, and it didn't time out right. And so, that role ended up being recast.

The first day [of filming This Is Us] I was like, "Chris, this is supposed to be the reverse. I was supposed to be directing you." He's like, "I know, I know. How crazy right?" He's so lovely. I've never worked with him on the show because I'm always with Kevin and Nicky so it was just really fun to get to know him a little bit. It's always great to work with an actor who's directing because I feel like they just so understand exactly what you're feeling in the moment. And obviously, he knows the show inside and out, and has such a great sense of humor. Every note that he gave was always such a great option to try. I felt like he just brought so much joy to every moment and he made it seem very natural to be in the director's chair.

Is this the last time that audiences will see Cassidy or is there more for her in the final chapter?

No one has told me what I can and cannot say, so I feel very nervous [laughs]. But I can say that it is not the last time you'll see her.

It's one of my favorite projects I've ever gotten to work on. I love the cast, I love the crew, I love the writers. I love working with Dan Fogelman, and I just love Cassidy. I think the character is such a complicated, beautiful person. Just as an audience member, I haven't really gotten to see a lot of female characters who have gone through what she's gone through. It's just such an honor to get to play her and to even get to do all the research and digging to try to do it the best I can possibly do it. I feel like I've learned so much and grown so much as a person by playing Cassidy. I just love every second of being a part of the show. So every time I find out that there's a little bit more for Cassidy, it's a great joy for me.

Does Cassidy end up agreeing to help Nicky with the construction of Kevin's future house? Will she be around to help Nicky?

She does say that she'll consider it. I think you have to ask the writers because I don't what I'm allowed to say [laughs], I never know what I'm supposed to say or not so I don't want to get in trouble.

This is like Marvel-level secrecy.

I know, I want to make sure not to ruffle any feathers as we're coming to the end of such a wonderful experience — but it's definitely a big maybe. It's just been so cool to be a part of the end of the show too. Obviously, as I've already said, the show's meant a lot to me, but I was very excited to find out that they wanted me to be a part of the final season.

This Is Us airs Tuesdays at 9 p.m. ET on NBC.

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