Guest stars and big storylines: the cast and creator offer a guide to the second half of the NBC drama's current season.

It's been two months since the This Is Us winter finale, and when the NBC series returns Jan. 14 with the second half of its fourth season, the same amount of time will have passed for the Pearsons on screen.

"We typically try to do a good job of catching the audience up on what's happened in the time they've missed," creator Dan Fogelman told The Hollywood Reporter after the midseason finale aired. "Kevin's been on his hypothetical search for true love and partnership for a month and a half, and we'll see how that's been going. Toby and Kate, what's happened since she's seen that text message? What's been the status for their last month and a half? We'll catch up on all of that stuff."

Tuesday's new episode, "Light and Shadows," will see Randall (Sterling K. Brown) travel to Los Angeles to care for his mother, Rebecca (Mandy Moore); Kevin (Justin Hartley) continuing his quest for romance; and Kate (Chrissy Metz) meeting husband Toby's (Chris Sullivan) Crossfit friends.

Below, Fogelman and his cast offer five things to know about the rest of season four.

1. Major Developments for the Family

The first episode back is a "special episode," Fogelman said. It's directed by cinematographer Yasu Tanida and sets up a new trilogy of episodes that will, as in season two, focus on a single Pearson sibling during the same time period for three consecutive weeks. It will also delve deeper into the memory issues Rebecca has been facing, which she told Randall at Thanksgiving that she was finally ready to address with a doctor. Those lapses are something Moore has researched heavily via podcasts, books and documentaries in preparing to play the oldest version of her character.

"I want to thoughtfully approach what Rebecca is going through at this stage in her life with as much care and consideration [as I can]," Moore told reporters during a Television Critics Association panel over the weekend. "I can’t imagine being in that position. I don’t want to speak too much to it, because obviously I want people to watch the season unfold and this journey that she’s on with her family, but I think it’s something we all have talked a great deal about. And I think in typical This Is Us fashion, we’re able to deal with issues across the board, I think, in a very graceful manner."

2. Randall's Anxiety

Fogelman said during the panel that the first of the trilogy will focus on Randall and his ongoing battle with anxiety.

"It's this intense, very unusual, specialized episode of our show that's about one thing, but it's also, in a strange way, about the marriage between Beth and Randall," he said. "I'm biased, but I'm really proud of what we've done this season and what we've got coming the rest of the season."

Added Brown: "It allows us to delve further into Randall’s mental health and how he takes care of himself, what’s right and what’s wrong about how he takes care of himself, and how he could possibly do a better job at that. The show’s going along, it’s like, 'Oh, this is nice. It’s a nice little episode of This Is Us.' ... And then this moment happens where you’re like, 'Oh, shit. This is about to go a little sideways.'"

Susan Kelechi Watson, who plays Beth, told THR that Randall's mental health will also affect Beth and their daughters, and the whole family will try to figure out how to deal with it together.

"How can we start to work through this? Because ... if Randall can't [take care of himself properly], Beth has to carry more of the load. That's not going to work anymore," she said. "It's untangling these original paths that they have created and forged in this family. How do we rewind and go, 'Okay, how do we do this going forward in a more healthy way for the both of us and for the kids?'"

3. Kate's Marriage

The midseason finale revealed that not only is Toby ripped from Crossfit, he's also texting about the distance between him and Kate with some of his buddies from the gym. That disconnect will continue to reveal a rift in their marriage when the show returns. It's "uncharted territory" for the couple, Metz told THR.

"We're going to get to see how they're going to navigate that. And are they going to navigate it? Because right now they're not on the same page, and they've been trying," she said. "It's not for the faint of heart."

She added, "The Kate-centric episode that's coming up in the trilogy is probably one of my favorite episodes ever, for so many reasons. We're going to learn more about the diagnosis of what's going on with Rebecca and what that means for the whole family."

4. Kevin's Love Life

Once again, Kevin has found himself in a phase of transition. In the present day, Kevin has told Randall that he wants to be a dad by 40, which is months away. But a flash-forward in the midseason finale revealed that while Kevin's fatherhood dreams are coming true — he has a pregnant fiancee in the other room — he and his brother are not on speaking terms.

In discussing Kevin's declaration, Hartley told reporters, "I think what he's saying was it's time to grow up and move on and actually realize I want a family. I want someone in my life to share life experiences with, to tell stories to. [Someone to whom] you say, 'Do you remember when?', and that person actually walked through that life with you and remembered it. I think that's really special."

It's all part of Kevin's path to maturity and self-improvement, Hartley said.

"Now I think he's starting to collect things in his life that mean something, that tell the story of who he really is," he told reporters. "He's carrying that weight with him and he's realizing what it is that he wants in life, which is super cool to see for me and to play."

While the mystery of who, exactly, that fiancee is will play out over the course of the season, Fogelman confirmed to THR that there will be an answer by the end of season four.

5. Famous Guest Stars

ICYMI: Your favorite family is back with a LEGENDary special guest. See you when #ThisIsUs returns Tuesday, January 14 on @NBC. pic.twitter.com/lV5psJht9j — This Is Us (@NBCThisisUs) January 9, 2020

John Legend is set to appear in the midseason opener (along with his new single, "Conversations in the Dark"), and Sophia Bush and Pamela Adlon will also guest star. Bush will be involved with Kevin's storyline, and Adlon will intersect with Randall's.

"Sterling has an unbelievable arc in the back half of the season, and she plays a very important — limited, but important — role in his story," Fogelman told reporters after the TCA panel.

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