Skylar Gaertner was just 12 when he landed an audition for the role of Jonah on a new drama called Ozark — he’d be playing the introverted son of Marty and Wendy Byrde, a suburban Chicago couple who would become money launderers for a Mexican drug cartel. Although he had been acting since the age of three, Gaertner wasn’t necessarily familiar with the acclaimed performers who would be leading the new series’ cast. “I had no idea who Jason Bateman was, to be honest,” Gaertner says of his onscreen dad and sometimes director. “I was just like, ‘Okay, that’s cool.’”

Gaertner is now graduating from high school at the same time he’s graduating from Ozark, the set he’s called home for the last six years, as the Emmy Award-winning series completes its final season. “The last day [of filming], there were definitely a lot of emotions,” he says. “You can’t help but feel something of the sense of finality, even though a lot of it doesn’t really sink in then.”

 Despite the intensity of the events that unfold on the crime drama, the on-set environment was anything but intimidating for the young actor. His first day of work was a photo shoot with the entire Byrde family — parents Bateman and Laura Linney, and Sofia Hublitz, who plays Jonah’s elder sister Charlotte — taking all the pictures that would be used throughout the Byrde house. “That was a funny first day because they’re like, Squeeze together, pretend you like each other, and I don’t know these people at all,” he says. “Jason’s always cracking jokes, and lightening it up a little bit. That was when you first started to realize that it was a really good group.”

That group grew to include Julia Garner as petty-thief-turned-criminal-mastermind Ruth Langmore, Jessica Frances Dukes as F.B.I. agent Maya Miller, and Felix Solis as the terrifying cartel kingpin Omar Navarro — gifted actors who helped Gaertner hone his craft. “There’s been so much to observe and absorb,” Gaertner says. “It made it the perfect environment where you could thrive. Everyone is rooting for each other. There are just so many people to look up to on [set].”

As the series unfolded, Jonah became the emotional center of the cartel drama. A sweet-natured boy, eager to help his parents, he developed a friendship with Buddy Dieker (Harris Yulin), the original tenant of the Byrde home, and bonded with his estranged uncle Ben (Tom Pelphrey). “My style was very much to immerse myself in his life as much as I could,” Gaertner says of how he approached playing Jonah over the years. “He shares a fair amount of similarities to how I approach the world.”

But in the series’ final season, Jonah finds himself at odds with his family. Still reeling after his mother facilitates Ben’s death — without showing any willingness to make the changes necessary to rescue their relationship — Jonah decides to help Ruth launder money for Darlene Snell (Lisa Emery), going against the wishes of his parents and the cartel, who have ordered Darlene to stop growing heroin. “I think it’s interesting because even after he becomes a power player, he’s sort of following the same trajectory that he was set on by his family,” says Gaertner of Jonah’s rebellion. “Everything he does is still in some way dictated by what his family has done, or continues to do.”

Viewers who have grown to love the Byrde family might be frustrated by Jonah’s choices and the implications they have for the clan’s safety and survival, but Gaertner believes they’re earned. “Having lived it from the perspective of Jonah, I always felt like that arc felt very justified,” he says. “It was always a matter of when Jonah would be pushed to the edge, not so much if.”

Gaertner was also delighted to have an opportunity to finally act alongside co-star Garner. “In previous seasons, we would complain that we only had, like, one scene together — What’s with that? Maybe there’ll be more next season. And then, finally, this season we were right. It’s been really fun switching over to the non-Byrde side. You just get to explore a different perspective.”

His time on the drama came to a close filming the startling car crash that opens the fourth season — Marty is driving the family in their minivan when a truck comes barreling toward them in the wrong lane. He swerves to avoid a head-on collision, only to flip the minivan. “There was a lot of weight to it,” Gaertner recalls of the sequence, though bidding farewell to his co-stars when he wrapped felt slightly surreal. “It was in a weird location because you’re in the middle of the highway, and all the trailers are lined up on the side of the road. To say goodbye to everyone, you have to run a mile.”

Looking back now, growing up on Ozark proved to be more nurturing for Gaertner than it was for Jonah. The actor completed both middle school and high school on set, taking his A.P. classes inside the Byrde family home. “I spent a lot of time in the bathroom because we converted that into the school room while we were filming, so I would be doing school in there,” he says. “Whenever someone came in the door, I’d say, ‘Welcome to our humble commode.’” 

Gaertner’s education also included some sage advice from Bateman, who is himself a former child star: “[Jason said] don’t be like he was as a child actor, particularly with running away from the set teacher and generally making their life miserable.”

Although Gaertner has moved on from the show, he says he hasn’t entirely let go of Jonah. “That headspace, it’s always a part of you,” he says. “[You] just absorb it into yourself. It’s still there somewhere.”

And he has plenty to remind him of his Ozark days. He constantly meets fans of the dark crime drama, sometimes in the unlikeliest of places. “There are people that you wouldn’t expect, like my grandparents, or the pastor at one of my churches, and they’re like, Oh, I love that show,” Gaertner says. He has mementos closer to home as well. “My dad and I started making birdhouses a while ago,” Gaertner says. “We made a few different kinds. We’re like, why don’t we make a Byrde-house birdhouse? It’s a pun — we had to do it!”