“Supernatural” leading man Jensen Ackles made his directorial debut on the show in the sixth season and then went on to direct a handful more. But after Season 11’s “The Bad Seed,” it seemed like he was taking a break from pulling double duty on the demon-hunting CW drama. His work in front of the camera kept him busy, as did the twins who turned his family of three into a family of five. But when the show was renewed for a 15th and final season, he knew he had to sit back in the director’s seat one more time.

“It was a little bit like the first time I did it just — just a little hesitant on a few things — but really, once I started rolling it was like riding a bike,” Ackles tells Variety. “We’ve got such a solid crew up here, from all the department heads all the way down. And this is not a crew that wants people to fail, and they certainly don’t want me to fail — or at least they put on that hat. So to be honest, you just have to do the work: You’ve got to put in the hours and make a lot of decisions, answer a lot of questions and then just hope that you’ve created a detailed enough roadmap than when you get on set you can navigate everything really easily. That’s what we did.”

The result is “Atomic Monsters,” the sixth episode Ackles has directed overall and the fourth episode of the final season. In it, Ackles’ Dean and Jared Padalecki’s Sam investigate the mysterious death of a teenage cheerleader and the disappearance of another from the same school.

“We see the brothers back together as they normally are, doing what they’re great at, and that’s saving people and hunting things,” Ackles says.

As has been tradition for Ackles when directing episodes of “Supernatural,” “Atomic Monsters” was the first episode shot of the season. This allowed Ackles to properly devote time to location scouting and prep work without having to worry about juggling these elements of his directorial duties with his usual actor responsibilities. It also allowed him to have enough time to sit with the script after breaking it down that he realized it was missing an element he really wanted: a big action sequence. So he created one.

“I took a concept in the beginning and really stretched it out to make it a bigger sequence,” he says, noting that showrunner Andrew Dabb always says, “The more action, the better,” which gave Ackles the greenlight. It’s “quite different than anything we’ve seen recently. It’s definitely more of a theatrical style, the way it was shot, the way it was designed. I had a lot of help in doing it.”

In it, Ackles directed himself in hand-to-hand combat and stunts, as well as a couple of key emotional moments, including bringing back “a character who’s one of my favorite characters of all time,” Ackles says. “It wasn’t even on the page. I said, ‘Can we make this character this person?’ And they were like, ‘If you can get this person — I believe they’re working right now.’ I made the call. He was literally working one day, had the next day off, so he flew in, did one scene, flew out and was working on his other project the next day.”

While Ackles and Padalecki always carry the bulk of the “Supernatural” episodes, “Atomic Monsters” does give Ackles a bit of a reprieve on-screen, thanks to the ongoing Big Bad storyline of Chuck aka God (Rob Benedict). Last the show checked in on him, he was trying to appeal to his sister Amara (Emily Swallow) because he wasn’t operating at full capacity and that impotence was rendering him useless and scared.

“For some reason on the page it read like a well-written B-storyline, but when we got it on its feet and started filming it, it very quickly became my favorite part of the episode,” Ackles says about the material with Chuck, “because of the contrast of emotion that Chuck brings. He’s kind of his funny, Chuck self, and then all of a sudden it gets really, really dark. And I think being able to have that balance in a page-and-a-half scene is a testament to how great the character’s written but also a testament to how great of an actor Rob is. He’s just so great at what he does, and I found myself forgetting to yell, ‘Cut’ because I was like an audience member behind the monitors.”

However, Ackles did also add a new level to himself as a performer in “Atomic Monsters”: by singing. Although Ackles’ vocals have been featured on albums dating as far back as the “Soap Sessions: Beatles Classics” compilation during his “Days of our Lives” days, he has yet to bring his musical talents into his television show — until now. The single “Sounds of Someday” off “Radio Company Vol. 1,” his debut album with long-time friend and musical collaborator Steve Carlson, plays over the climax of Dean and Sam’s run-in with the monster of the week that they are hunting.

“To be honest our editor inquired about it. He said, ‘I know you did some music over the break, do you think we could take anything and plug it in?’ I wasn’t angling for that, I wasn’t pushing that, and in fact we didn’t even tell Bob or Andrew or anybody. We just floated it in there and waited to see if anybody said, ‘I don’t really care for that song, I don’t know who that is,'” Ackles says. “And nobody said that.”

In addition to “Sounds of Someday” Ackles says he had a few other music cues in his director’s cut, including a big one at the end. “Two of the three got taken out; mine was the last one standing,” he says of his new single. “That was a small victory. That was a nice vote of confidence, especially from a show that prides itself on music so much.”

Part of the reason Ackles has enjoyed being a part of “Supernatural” for 15 years is because the show allows him to try new things, both in front of and behind the camera. And before the series signs off in May, Ackles still has one more new box he might like to check: creating the story for an episode.

“We have an idea for an episode to explore,” Ackles says of himself and Padalecki. “When the show explores its wacky side I think we get a lot of really, really good stuff. And he and I and Richard Speight have been kind of kicking an idea for an episode around for a year and a half, two years now.”

Citing previous one-off humorous episodes including “Changing Channels” and “The French Mistake,” Ackles says this idea is not of the lore, which means it might not end up making it in the final season after all.

“It is a lofty idea, and to be honest we’re shooting such a concentrated season because we’re trying to pack so much into the last episodes,” he says. “I’m not going to count on it because obviously we’re not the writers of the show — that’s not our job — and I would never force our ideas on the writers, but that would be a really fun box to check.”

And, he reiterates, if there’s not room to do it now, “maybe we’ll save it for the reboot.”

“Supernatural” airs Thursdays at 8 p.m. on the CW.

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