SPOILER ALERT: Do not read if you have not yet watched “A Hell of a Week: Part One,” the 11th episode of the fourth season of “This Is Us.”

It was a moment that made actor Sterling K. Brown scream out-loud when he read it in the script: his “This Is Us” character, Randall Pearson, arrived home from a trip to deal with his aging mother’s (Mandy Moore) health, checked on his sleeping wife and daughters, and headed back down to the kitchen, only to catch someone breaking into his house in the act.

That cliffhanger from the midseason premiere episode, entitled “Light and Shadows,” paid off in the first-part of the fourth season’s Big Three trilogy episodes, “A Hell of a Week: Part One.”

Randall, who was already stressed out about his mother’s unclear diagnosis, took a few solid, deep breaths to steady himself and then did what he does best: He talked to the guy. He told him he was a councilman and the police were already on their way because the guy had tripped a silent alarm. He said the house was covered in cameras, recording his movements as they stood there in a face-off. He tossed him some money from his pocket. He told the guy he didn’t want any trouble. And it worked. The guy grabbed the money and ran out the back door without physical incident.

But physical harm is only one thing that can happen to a person in such a situation.

Already someone living with anxiety, Randall spun out in a way never before seen from him. Outwardly, he remained calm in front of his loved ones and co-workers, and he went through all the right motions of actually calling the cops, getting an alarm installed and sending his family to a hotel for the night. He threw himself back into work — and running. But the inside of his mind was far less quiet than his outward appearance, and he stopped sleeping, started obsessively checking the security app on his phone, went off on a mugger (which resulted in HIM getting injured) and eventually broke down behind closed doors.

“I’d known throughout that the way Randall uses his sense of humor is often to sort of deflect, to sort of be accepted, to be liked, to fit in. There’s always a struggle to find comfort in his own skin. His sense of his own blackness is part of that, but then there’s this underlying anxiety that things will not work out. I think it’s part of the reason that he pursues perfection the way that he does, and it probably is the thing that has inspired him to be an overachiever,” Brown tells Variety.

Brown has been portraying Randall across a couple of ages for the past four years, but he still manages to find surprises in the scripts and new insights into the character from outside sources. After watching a documentary about Diana Nyad, the journalist and author who attempted to swim from Cuba to Florida four times before finally succeeding in 2013, Brown says he found himself relating her journey to Randall’s: “Someone that driven is not just running towards something or swimming towards something, they’re also simultaneously swimming away from something,” he says.

Here, Brown talks with Variety about the physical demands of an episode like “A Hell of a Week: Part One,” why he thinks Randall has been so reluctant to go to therapy his whole life, and what his new bout of PTSD means for his relationships with his family.

Seeing Randall faced with this external threat had to force you into a very intense mindset. How did production work on the last bit of “Light and Shadows” and the start of “A Hell of a Week: Part One”?

The director of [Episode 4.10] was our director of photography, Yasu Tanida. He shot the ending, and then Kevin Hooks, who directed [Episode] 4.11, they were both on set that day. We shot one scene and then would take a quick pause, there’d be a reset of cameras, and we’d continue into the beginning of the next episode. So we did cross-shoot so there was continuity in that moment.

What were you channeling for this very intense scene that also triggered Randall’s anxiety into a much more concerning place than the show has previously explored?

There’s conversations with a few people that I had. A couple of friends had had break-ins, and not necessarily coming face-to-face with the home invader, but just the feeling of being violated and thinking that there is one place that is your place — that is your safe space — and now that safe space has been taken away from you. Those conversations parlayed into, “OK so what if you do come face-to-face with the person who’s not supposed to be there?” Also, there’s this level of exhaustion, there’s still the “What am I going to do about my mom?” and the sadness about what could possibly be her future. That, and then you’re thrown completely out of your comfort zone, but you still have to protect. There’s a fight or flight thing that happens in us where we revert back to our limbic system, and it’s like, “OK, there’s somebody in my home and my wife and my children are here; whatever happens, they have to be safe.” And so, you put up a front; you peacock; you make yourself bigger than what you actually feel on the inside in the hopes that that largess will scare that person away. That’s what Randall is doing in that moment. He’s scared out of his f—ing mind, but he could not live with the possibility of harm coming to his family, so for their sake, he’s got to make himself big.

But the moment before he does that, when he’s just taking those deep, steady breaths to slow his anxiety and let him regain control, was that on the page or was that something you developed as a coping mechanism?

That was just me.

So where did that come from?

I know that there are times in which one feels nervous or stagefright or something of that nature, and the first thing that people tend to do is hold their breath. But the only way that I know to allow something to pass through me is to literally breathe through it. And so I think that there would have been a halt in forward momentum if I stopped breathing. I had to keep going forward. In order to make the whole thing work — in order to make this person think the police are on the way, that he’s already on security camera — I have to keep breathing. Because if he sees too much fear, the jig is up. I don’t know but that’s really probably one of those unconscious things that you do in the moment that just felt right, and you go with it.

Randall’s anxiety has manifested onscreen before, but never quite to the level in “A Hell of a Week: Part One.” How does learning how he experienced these symptoms so young, when he was learning to sleep in his own bed for the first time, change or inform Randall in new ways from how you’ve already been playing him for four years?

We had seen things: We’d seen Lonnie Chavis [as Young Randall] planning how he wanted to attack Halloween and how, when things in his plan are not adhered to it causes him to have a bit of a moment, if you will. If he’s not having an attack — if it’s not anxiety — he’s having a moment. And when he wears his Jordans to impress his school teacher and then his teacher is about to turn him in, again there’s a moment. And so when seeing the 5-year-old version of Randall, I actually went into the writers’ room and told them, “I think you guys created this pretty consciously, but what it has evoked in me throughout the course of [Episode] 4.11 is that there’s a baseline level of fear that this man has lived with his entire life.” And there are times in which it seems quote-unquote managed, and then there are seems when it seems like it’s barely able to remain under the surface — this episode being one of those moments. His mom is sick and he doesn’t know exactly what it is, but the prognosis at present is not one that he necessarily wanted to hear. And now his home has been violated. The possibility of something happening to his children or his wife, there is this idea that I think Randall holds onto that as a man — and I think that Jack Pearson was probably the model for it — [of] if I cannot take care of my family, then who am I? And what worth am I? Throughout the whole episode, he was just exhausted by fear: carrying around the home security app and checking it incessantly, almost not able to not check it, even when he was in the Town Hall meeting it went off a couple of times and he was like, “Ahhh.”

Niles [Fitch] as [Teenage] Randall was dealing with the PTSD of losing his dad in the fire, and the Randall now is dealing with, “OK how can I move forward?” He’s found a wonderful partner to share his life with in Beth, he takes wonderful physical care of himself and running has been a release for him up until now. Did he do a good thing by accosting that mugger? Yeah he did. But did he have to beat the crap out of him? Probably not.

Well, he deserved it. It’s not like he was some kid.

No not some kid, for sure, but for Randall, I believe — or at least what was going on for me — was for someone who lives their life with that underlying level of fear constantly just under the surface, it was also an opportunity to not be afraid; it was an opportunity to take all of that fear and turn it into aggression and release it. And I think it scared him. And hopefully it scared him to the point where he recognizes that what he’s been doing to survive up until this point may not be enough; he may need to explore some other options.

Darnell (Omar Epps) suggested therapy as an option. Historically it has been rare to see African American characters partaking in therapy, but Randall grew up in a family that did so much talking, so what conversations have you had with the writers about why Randall has rejected the idea all these years?

I think the easy answer is Jack Pearson. Jack Pearson plays things pretty close to the vest: if ever there’s a dude that takes care of this own problems, it is he. I also think he follows his father’s template in that the person that Jack allows the greatest access to his life is the person he chose to share his life with, Rebecca, and I think the the same thing holds true for Randall: Beth is his home base. If he can’t talk to his wife about it, then he probably can’t talk to anybody about it. I will speak to, from a personal standpoint, the cultural difference for me from Randall is that there’s the idea as a black person in this country is that life, of course, is hard: there is racism, there is prejudice, there are things that you have to deal with that other people don’t — but don’t spend too much time whining, complaining, et cetera; figure that s— out and keep going. And so the idea of, “Well, I might need to see a therapist” seems soft, it seems like you’re not recognizing that of course life is hard; it’s hard for all of us out here. That’s not what Randall’s template is, per se — although Jack, from a socioeconomic standpoint is like, “Life is hard.” He is Romeo to Rebecca’s Juliet: he is from the other side of the tracks — and he has found a way to compartmentalize his life that allowed him to live until he ultimately expired in his fire. I think that’s Randall’s template: to figure it out. Randall became the man of the house and he figured it out. Also, being a highly intelligent individual, I think it’s sort of beyond his scope that somebody could understand him better than him. And I think that’s probably the plight of a lot of highly intelligent individuals: “I don’t know if this person that I’m sitting across from with their legs crossed and their little notepad is actually smart enough to figure me out.” So I think those two things — Jack Pearson and Randall’s own intelligence and reliance on his intelligence — may be some of the things that kept him from seeking help outside of his family.

All of that sounds exhausting, which you mentioned it is for Randall, but it also sounds exhausting for you as an actor. Between the tension you have to carry in the scenes and then the actual running you had to do, how do you adjust to the physical demands of something like this?

They’re different. Brown is a bit more cantankerous during said episodes. There’s a level of tension in my body that I feel at the end of the day. There’s an exhale; you’re waiting — literally — to exhale at the end of the day. And I realize how fortunate I, Sterling, am, in that there have been times in my life where I have been particularly hard on myself. Now is not one of those times; I feel like I practice grace with self first because you have to be graceful with yourself in order to be graceful with others. But there’s a deep level of empathy for friends; for family members that I have that live with anxiety, bipolar, schizophrenia, other mental disorders. It must be exhausting to be scared all of the time; it must be exhausting to not feel fully comprehended. And so, during the course of this episode, almost on a nightly basis, I had that feeling of, “I’m tired.” The running was probably the most energizing part of the episode because I got a chance to just let go. There’s a wonderful release, there’s something meditative, there’s something that you feel like you’re being productive — and you exhaust yourself to the point where you’re not exhausted but you can’t hold onto unwanted emotion. That’s how I feel, and I think that’s how Randall feels for the most part when he runs.

Randall called his brother (Justin Hartley) at the end of the episode to admit he wasn’t doing well, but the next two episodes in this “A Hell of a Week” trilogy are not centered on Randall. So how much do we see the trickle effects of what he’s going through in the immediate future, and how much of a help can he be for his siblings during their own hell weeks if he’s not 100% OK?

Well, similar to how they were relatively absent from his episode, he’s relatively absent from their subsequent episodes. And then you’ll see the totality of everybody having some heavy s— going on in their lives. What I love about it is that when the three episodes are complete, the three of them get to come together, and you see how they are able to connect and how they are able to help each other through their problems.

And seeing that Beth in college was such a steading force and almost a caretaker for Randall put a lot of their relationship into a new perspective. Going forward with Randall still struggling, how much of that behavior is reflected in present day?

That question will be most succinctly addressed in Episode 4.15. I won’t answer it, I will just refer you to that episode for your answer!

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