Project Blue Book is back -- and bigger than ever.
The History series returns for its second season on Tuesday and is kicking things off with one of the most well-known conspiracy cases in American history: Roswell.
"We're getting straight into cases people will have some familiarity with," star Aidan Gillen told ET. "And, why not?"
Project Blue Book, based on the real-life investigations conducted by the U.S. Air Force from 1952 to 1969, focused its first season on Dr. J. Allen Hynek's (Gillen) introduction to the world of UFOs as he and his partner, Capt. Michael Quinn (Michael Malarkey) learned the delicate balancing act of what to tell the public -- and what to tell the government -- about their investigations. The first season covered a few high-profile cases, but none with the same name recognition as Roswell or Area 51, which are featured in season two's first three episodes.
"It is bigger and better," Malarkey said of Project Blue Book season two. "But I feel like it's also much more nuanced and fine-tuned as a machine. We've really hit our stride and our sweet spot as far as how we can tell these stories."
"Roswell is still -- we're still unraveling this. There's still books being written about it, new takes. And the thing with Roswell is almost everybody who was an actual witness is pretty much dying out. So, you have secondary witnesses or sons relaying information that their dads told them or things like that," he added. "I think the way we visit Roswell is in a similar way of rewinding or going back and reanalyzing, opening back up this case, and I think it's such a clever way to kick off the series."
"Yeah, and we actually had to rewind, because we started off in 1951, and the Roswell incident was in what, '47?" Gillen chimed in. "So, our writers found a clever way of enabling us to show up in Roswell and backtrack and roll back the tape a few years."
Playing around with the timeline has also allowed season two of Project Blue Book to follow Hynek in his role as a consultant to the 1977 film Close Encounters of the Third Kind.
"One of our episodes deals with the Robertson panel, which was a real inquiry where the CIA went head to head with Project Blue Book and required them -- or put it upon them -- to prove their validity and their worth... was quite humiliating for Hynek and for the Blue Book team," Gillen shared. "We do tell that story, but it's framed around the shooting of Close Encounters in 1977, which Hynek was a technical consultant on. [Steven] Spielberg was inspired to make Close Encounters from the readings of Hynek's books, and just the popularization of UFO phenomenon, which Allen Hynek did really push into the forefront of pop culture by the 70s."
"So, to play this character 26 years in the future from where our main story takes place on the set of an iconic film, which is one of my favorite films of all time, was pretty splendid," he raved.
The actors have nothing but praise for the creative team behind Project Blue Book, who have upped their game for season two. Everything from the cinematography to the costuming to the storytelling stands out.
"Going back for your second season, you've got a lot of things to your advantage in that we know each other, we know each other well, the writers know us, we know what works, we know what people like. We know what areas we can improve on, we know what's fun, what's not fun, et cetera," Gillen explained. "And we have a myriad of stories to work from."
Malarkey and Gillen's own relationship has also evolved through filming the series. They met just three days before shooting season one, but have since developed a friendship -- which has extended to their characters, affectionately dubbed HyneQuinn.
"Our relationship is a lot more dynamic, and we're more on [the same] side in a way, though there's still sh*t that goes on," Malarkey said, seemingly hinting at Quinn's new relationship with Susie (Ksenia Solo), a spy who tried to gain information through Hynek's wife, Mimi (Laura Mennell) last season.
"When you meet these two guys together, at first they're at odds with each other, and towards the end of season one, we seem to be on the same page in ways. But it should never be as settled as that," Gillen noted, teasing that "friction" is an important part of Quinn and Hynek's relationship.
"The characters have been through a lot, which always means something in terms of where you can go dramatically, but we've also been through a lot, just as workers, together. And we'd like to feel that there's a lot of stuff we can do more without words, or with less words. We will have this more nuanced and in that respect, more interesting, relationship," he offered.
Season two of Project Blue Book premieres Tuesday at 10 p.m. ET/PT on History.