This Is Us: Everything you need to know about season 3

What will Kevin learn about Jack in Vietnam? Why is Toby depressed? Who was the “her” that old Randall told Adult Tess that they needed to see? These are just some of the questions hanging in the air as season 3 of This Is Us inches ever closer to its premiere date. (Sept. 25, 9 p.m., NBC.) There’s a lot more than mystery and misty eyes in store, so start scrolling to see what else you can expect from the new adventures of the Pearsons.

The season premiere takes you back to see the first date between Jack (Milo Ventimiglia) and Rebecca (Mandy Moore). “People expect it to be a straight line to finding one another and living happily ever after,” teases Moore, “and that may not be the case.”

This season premiere, like the ones before it, takes place on a Big Three birthday — Kate (Chrissy Metz), Kevin (Justin Hartley), and Randall (Sterling K. Brown). This time, they turn 38.

Beth will not be pleased when she detects a budding romance between her brother-in-law Kevin (Justin Hartley) and her cousin Zoe (Melanie Liburd). "Somethings will surprise about the reaction of Beth and Randall through the relationship," says creator Dan Fogelman.

Toby (Chris Sullivan) and Kate will decide to embark on another attempt to have a baby, as indicated in the first footage released from season 3. “Having a baby is something that is life-changing, and two people just want to hope that they can have a baby,” Metz told EW. “Whose fault is that? Maybe there’s something going on physically with Toby too? Who knows? Those things might not have been talked about or addressed because we keep our secrets and we’re ashamed of them.”

Toby has fallen into a depression — something he has struggled with in the past — and viewers will learn whether or not it's related to the newlyweds' attempt to expand their family. In any case, it's ground that Sullivan is eager to explore. "You have to continue to develop your tool kit for relating to your person, so as long as they stay in it, stay in the ring, it seems like they have a pretty decent coping mechanism as far as navigating stuff like this. "

The show will delve into the mystery introduced in the season 2 finale: Who is "her?" And why don't old Randall and adult Tess (Iantha Richardson) want to visit “her"? It sounds like answers will be coming sooner than later (later being the length of the how-Jack-died mystery). Season 3 involves a “journey to fill in the pieces of the puzzle,” Fogelman says. “I would be so bold as to say the flash-forward puzzle pieces will fall into place by the halfway mark.”

Beth isn’t dying, despite any fan theory that you may have heard in regards to the flash-forward mystery. Which is good news for Watson's mother. “My mom was like, ‘I’m not going to watch this show next season,'" she told EW. “I was like, ‘Why?’ She’s like, ‘Because they’re going to kill you, and I don’t like it.’ And I was like, ‘Mom, they’re not going to kill me!’ Dan [Fogelman] and I spoke about it — they’re not going to kill Beth. She’s going to survive. It feels good to know.”

Seriously, though, before we move on, can we have one more hint about who she might be? “It is someone that we have met over the first two seasons,” teases Brown, “so it won’t come out of nowhere.”

Ron Howard's WWII movie starring Kevin and Sylvester Stallone finally will be released. “"Does he win an award?" says Hartley. "How’s he going to deal with that? Does his sobriety get in the way? Does it help him? And what if the movie doesn’t do well, how does he deal with that?”

During his press tour for the movie, Kevin will cross paths with familiar faces including Natalie Morales and Terry Gross.

Kevin, who was last seen headed over to Vietnam, will learn intel about his deceased father, Jack, who served in the Vietnam War. "It's a healing thing for him," says Hartley. "He’s going to get a lot of information, some stuff that he didn’t know and didn’t expect. And it’s going to jar a few things.”

You don't know Jack in his entirety, but this season will aim to paint a "fuller" picture of him," according to Fogelman. The revelations about his time in Vietnam came as a surprise to Ventimiglia. "I really didn’t see it coming," he told EW. "I went, ‘Oh. Holy s—. Holy s—. Holy s—!’ I kind of felt like Daryl walking out of the backroom card game with all the money, like, 'This is going to be so good.' There is a lot to Jack’s history that shapes who he ultimately becomes.”

Michael Angarano has been cast as Jack’s little brother, Nicky, who served with him in Vietnam — and presumably died there. “That first time we see Nicky is going to paint a pretty clear picture of what his demons are — and what his struggles in life are,” says Ventimiglia. “But just like classic This Is Us, we’re going to bounce around in time and see a greater look at this new Pearson.”

Some of the season 3 Vietnam story line will be shot on location in Vietnam. There will be at least one standalone episode about Jack's time in Vietnam, and the story will be threaded throughout a chunk of the season. More evidence that Fogelman is taking the Vietnam plot very seriously? He tapped Tim O'Brien, who wrote the Vietnam war memoir The Things They Carried, as a consultant for the story line.

We’ll see Rebecca and the teenage Big Three struggle to move on in the months after Jack’s death. “It’s tempers and bad behavior from the kids, and disconnection,” says Moore. “Rebecca is trying her level best to push forward and pick up the pieces of their shattered life.”

Randall and Beth will have their hands full this season, working on rehabbing William's old building and trying to help Deja after her Mercedes-attacking outburst.

You've met Deja's mother, but there's another parent to learn about: her father. "Obviously, Deja has had almost no relationship with him, but she may know more about him than we previously let on," executive producer Elizabeth Berger told EW. "So, we’ll get to know a little bit more about what that relationship is moving forward."

Randall and Beth also will have to push through some marital strain. “They hit a snag where they want different things out of life,” says Brown. “You gotta work that s— out, so you see Beth and Randall working that s— out.”

Daredevil actor Rob Morgan will appear in several episodes as a city councilman who represents the district containing William’s building.

Malcolm in the Middle alum Jane Kaczmarek will pop up in an episode as a university professor and scientist who is described as intelligent, warm, and down-to-earth.

The now-deceased William (Ron Cephas Jones) wasn't as big of a presence in season 2 as everyone hoped, but expect to see the character early on in the season. "Our second episode has a big William story, and we have others coming," says Fogelman. "Of our first seven or eight episodes that we've got written right now, he's a substantial part of three or four of them."

Individual episodes will drill down on the backstories of Beth (you'll meet more of her family), Toby (don't forget about his brother, who was a no show at his wedding), and Miguel (see next slide). "Our plan is to really fill them in quite a bit,” says Fogelman. “There's a real opportunity to learn more about their pasts in this season and that's something we're planning on doing for all three of them.”

What might you learn about Rebecca's second husband? "Miguel (Jon Huertas) was married, Miguel had a family, but we haven't heard much about them," hints Fogelman. "It’s interesting that we haven't seen them a lot in the present-day Miguel and Rebecca story line."

Eager to preview the season 3 premiere through the magic of still frames? Head over here.