"Orphan Black" star Tatiana Maslany teases "absolutely enormous" season 3

"Orphan Black" capped off its second season last year with a bombshell for Tatiana Maslany and her clone characters: they're not alone.

The revelation that there are male clones, too (the self-aware, militarized clones known as Project Castor), raises the stakes even higher for the cult-favorite BBC America sci-fi series, which returns for its third season on Saturday. It also means Maslany's not the only one juggling multiple roles -- Ari Millen now joins her in that very select clone club.

"I was really excited about the prospect of it because I think Ari's such a strong actor, and I think what they offer us is another exploration of nature/nature, a different perspective, a different kind of experiment," Maslany told CBS News during a recent conference call with reporters. "The Leda clones were raised separate from each other, so for them to discover each other is their journey, and to come to terms with the fact that they're clones is their journey. But the Castor clones were raised self-aware and in a unit, so there's a very different experience that they bring to the equation."

Maslany has been playing Sarah, Helena, Alison, Cosima and the rest of the Leda clones (nine of them in all -- that we know of so far, at least) since the show began, with her characters often overlapping in the same scene and, sometimes, pretending to be one another. Speaking from a remote location in Canada where she's shooting a film, the actress said she and Millen had discussions about the challenges that work brings.

"Ari is an amazing actor and definitely had his own process in terms of what it was for him. But when you're facing something like this, it's always nice to have somebody as an ally and we definitely had an open discussion going anytime there was something that came up," she said. "When I saw his first clone scene, I saw a rough cut of it and it was unbelievable. His understanding of the technical side of it, while also being able to be present and be relaxed was really - I was amazed by it, he's kind of a natural at it. It's very cool to watch someone else go through this, the same process that I did."

Maslany shared that there will be a "shift towards the Castor clones" this season, and viewers will get to learn more about them. There will also be guest stars (James Frain and Justin Chatwin among them, though she wouldn't disclose much about who they're playing), plus more time spent with supporting characters like Mrs. S (Maria Doyle Kennedy), Donnie (Kristian Bruun) and Paul (Dylan Bruce).

And Felix (Jordan Gavaris), who's already grown closer to Alison in addition to his bond with foster-sister Sarah, will be developing a new friendship with Cosima.

"The two of them have sort of been a little bit at odds for some reason, and not because of any overt thing," Maslany shared. "So we got to explore a more slow burn sort of relationship between the two of them. They have so much in common in terms of being lonely, and there's just like, a heartache in the two of them...They're kind of unlikely coming together of two people."

With all the raised stakes, including the addition of the Castor clones and the abduction of Helena (an act of betrayal by Mrs. S and Paul that "forces Sarah into some of the most difficult decisions she's had to make so far"), Maslany says fans can expect "an absolutely enormous season."

"The mystery continues to unravel, and like in seasons past as soon as you get a little bit of a clue into what's happening the rug gets pulled out from under you and you have a thousand more questions," she teased.

The actress also spoke about the loyal following the show has amassed (fans call themselves the #CloneClub), and interacting with them at Comic-Con and other conventions.

"Those events are the most exciting part of the 'other stuff' of the job. It feels amazing to get to meet the fans and interact with them in a personal way and for them to get to tell us how the show has impacted them is unbelievable," she said. "We've always been really humbled and inspired by our fans and by their dedication to the show and also how it changes their own lives and their own personal journeys. It's incredible - you don't expect that when you're doing a TV series to have that kind of impact. We're lucky to be in a world right now where we're able to interact and discuss important things with our fans. It's totally gratifying. "

"Orphan Black" returns Saturday, April 18, at 9 p.m. ET on BBC America.