EW – The last time you saw Kevin Pearson (Justin Hartley), it was at the end of the season 2 finale of This Is Us and he was headed to Vietnam with his new girlfriend, a.k.a. Beth’s cousin, to learn more about Jack’s life there during the Vietnam War.

The next time you see Kevin Pearson, he’s not going to get those answers, but sometime after that, he will start to. “He’s going there — it’s a healing thing for him — so he’s going to get a lot of information, some stuff that he didn’t know and didn’t expect,” Hartley tells EW. “And it’s going to jar a few things.”

What Kevin uncovers about the time that his deceased father (Milo Ventimiglia) spent overseas during the war is “super heartbreaking ” and “shocking,” according to Hartley. “It’s not what anyone is expecting,” he says. “No one is going to see it coming. It’s ambitious stuff…. Here’s the cool thing about it: At the end of season 3 when you go back and watch the beginning of the series, you’re going to [be] like, ‘Wow, it all works,’ but you never would see any of this coming. I don’t know what those writers are eating, but it’s brain food. They’re brilliant.”

Hartley also offers a few hints about Kevin’s budding relationship with Zoe (Melanie Liburd) by asking questions instead of answering them. “Do they fall in love quickly? Are they friends? Are they lovers? What’s going on with that?” he says. Whatever this connection is, his sister-in-law, Beth (Susan Kelechi Watson), apparently will have trouble embracing the idea that her brother-in-law — yes, the man who got pulled over for a DUI with her daughter in the car — and her cousin are interested in each other romantically. “It’s not going to go over [well],” says Hartley. “What do you think it’s going to be — smooth or rocky? I think rocky. Rocky’s more fun.”

And since we’re throwing out questions, what is going on with ex-wife-turned-girlfriend-turned-ex-girlfriend Sophie (Alexandra Breckenridge)? “Does she come back [to him]?” he continues. “I don’t know why she would come back. Does he want her back? I think she’s probably done at this point.”

In other Kevin news, Hartley has even more questions for you to ponder about the fresh-out-of-rehab actor’s war movie with Ron Howard. “Does he become a massive celebrity or is the movie a flop?” he says. “It’s a Ron Howard movie, so it’s not going to be a flop. Does he win an award? 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?”

Those questions and more will be tackled when This Is Us returns to NBC for season 3 on Sept. 25.