Supergirl: Katie McGrath Discusses Luthor Sibling Rivalry

Lex Luthor has finally arrived on Supergirl, and that spells trouble for his sister Lena. Since he reentered her life, Lex has stolen her research as well as her research assistant Eve Teschmacher -- who, it turns out, was on his side all along. However, when he returned to cure Red Daughter, Lex left behind an even more determined Lena. Now, she will stop at nothing to bring him down, and that means she will work with Supergirl and the DEO to stop him.

Speaking to CBR, Lena Luthor actor Katie McGrath revealed how Lex's latest plan has inspired his sister to take a more proactive role in his capture. She weighed in on Jon Cryer's version of the character, why his performance completely surprised her and what it's like to work with him. She also teased the aftermath of Eve's betrayal, why that moment will make Lena more dangerous than ever, how her use of the cure impacts her relationship with James and more.

CBR: You've played Lena for years now, so you must have built up some version of Lex in your head. How does Jon Cryer's version compare?

McGrath: He smashed it. Any expectations I had, he completely threw them out of the park, because I think people have a preconceived notion of Jon Cryer because they've seen him do so much comedy. There is such a comedic element often to super villains that you think, "Oh, they've cast Jon Cryer. That's kind of where they're going." And then, when he came on set and he was Lex, I was like, "Oh my god, we are in for a fucking surprise here. This is something completely unexpected."

He was so calm and so arrogant and so gentle that when he played the megalomaniac, crazy moments of Lex, you were completely shocked and shook by it! Because the first few scenes I had with him were all when he was very sick and he was in the wheelchair and we were doing all the stuff when we had cancer, so when he actually came to playing Lex as a super villain, it was so unexpected. I had so in my head gotten this idea that this version is quite gentle, a little bit snarky.

You know, I thought I had sort of figured out what he was playing. And I think that's what's so amazing about what Jon Cryer has done. He has given you a Lex that was unexpected, but brilliantly crafted and nuanced and you kind of think he's sympathetic, but then you think he's crazy, but then you're like, "Oh, I'm enjoying how evil he is!" I don't think anybody thought that Jon Cryer was going to do that. He just completely blew all of us away and we realized how completely lucky we are to have him. [laughs]

He's pretty unbelievable and also just the nicest man. I cannot say any more positive things about him as a person as well.

Lena obviously has a soft spot for Lex, despite everything that's happened between them. Do you believe that's something she could ever let go of?

I don't know! I mean, I want to think that she could. I want to think that somebody is always capable of standing up to people who hurt them again and again, but there are those people in our lives that can always get under our skin and often they are family. You were created, often, as a person with them from a very young age. You know, the imprint is made, and you spend the rest of your life dealing with the results of that imprint as a child.

Lena had very, shall we say, traumatic early years and she's still dealing with the results of those and Lex is such a huge part of it. I think that's her Achilles heel, between Lex and Lillian, these people who were supposed to love her unconditionally but then didn't. I think that has shaped her as a human and so therefore, in her later years, of course they're able to get at her and get under her skin like no one else can. I like to think and I hope in years to come she'll be able to stand up to him, but it's family. You know yourself. They can get you when no one else can!

NEXT PAGE: The Aftermath of Eve's Betrayal

Lena put a lot of trust in Eve Teschmacher. Did you see that twist coming?

God, it was so delicious, wasn't it? It was so good! You know, they waited so long, because -- when you see Eve Teschmacher -- you're like, "Oh, okay, well, that's with Lex," but she was on the show for two years! Andrea [Brooks] was on the show for two years before they pulled the trigger on that one. I just think it was the smartest way to do it. That made it so unexpected and so out of nowhere, so the shock you see and betrayal on Lena's face in that scene I kind of feel is the same feeling the viewers must have had watching that, who had been with the character for the whole two seasons. I couldn't think of any more clever way to do it... When we finally got to it and we were doing that scene and Andrea puts the gun up and goes, "Sorry, not sorry," I'm just like -- shivers. Chills went down my spine! It was just the most delicious, dramatic betrayal of all.

How does Eve's betrayal affect Lena moving forward?

I mean, I think it's going to do two things: first of all, it's going to focus Lena to catch Lex and to catch Eve. She's going to feel responsible. She had a viper nestling at her breast type of thing, you know what I mean? So she was the one that did this. She nurtured it, and she's going to feel responsible for Eve and all of what she has done moving forward... Let's just say she's going to feel responsible for stuff moving forward because of her past relationship with Eve and what she's done with Lex, that she's cured him.

Moving forward, into the second half, Lena feels that this is her fault. So it's going to focus her very, very much to fix that, to go out and to find Lex, to find Eve, to catch them, to right the wrongs, to sort of allay her conscience because she feels responsible. I think a focused Lena is a very dangerous thing. She's a really smart, capable woman, so when she gets an idea in her head, I think all should beware.

At the same time, I think what you're going to have is Lena moving closer to the ones that she does trust, which again is a very wonderful thing, and bittersweet to the viewers because she's going to hold onto the friendships that she holds dear, like Kara. For the viewer watching that, the viewer is going to know that while Lena is holding onto her friends deeper, that they all also are keeping secrets from her as well, like Eve was. They're not evil secrets and they're not malevolent, but it's still going to be hard to watch somebody hold closer to people she cares about who are also lying to her. So I think that's what will make it so wonderful to watch, but also very sad for Lena.

NEXT PAGE: Working With Supergirl & James

Lena has been working with Black Kryptonite for some time now, so she's got to have some thoughts on Red Daughter. Tell me a little about how this Kryptonian doppelganger affects her moving forward.

Again, I think it's something that she feels responsible for, but also I think with being an ongoing aspect of her personality is that she keeps trying to do things for good and others keep taking what she's doing and perverting it. So, you know, the image inducers are taken and used against her. The Harun-El [Black Kryptonite] is not used against her, but used for malevolent purposes. You know, she is trying to figure out things that are going to help the world and help humanity and other people keep taking her inventions and her discoveries and using them to destroy the world.

I think, again, this happens with Harun-El, that she's trying to cure cancer -- she's trying to literally save people's lives! -- and she has discovered that she can create the thing that can ultimately destroy all life, which is another Kryptonian, if used wrongly. So I think constantly she's battling against trying to do good and ultimately feeling like she has destroyed everything. So, again, this focuses her to try and right all these wrongs that she feels responsible for.

Lena's relationship with Supergirl has been tenuous at best this season. How does that change when Lex enacts this next phase of his plan?

I think what happens is that you start to see that Lena and Alex and Supergirl all have a common enemy and a common goal. This has been something that's been a seed since they sort of split from their friendship, is that even though they come at things from two totally different, opposing sides, they ultimately have the same goal. They're ultimately both trying to protect humanity and save people. It's like one is the right wing and one is the left wing, you know what I mean? They both have the same goal; they're just coming at it from different sides. I think that's what you see here when they're ultimately all trying to just catch Lex and deal with Red Daughter and figure out what he's up to. So they all have the same goal, so they can put aside their petty differences and work together for the greater good.

The tension between Lena and James came to a head a couple weeks ago, when his life was in danger. How do her recent actions impact her relationship with him?

I think it's really difficult for James and also for Lena, because she made this decision, this decision born of desperation, because a person she loved -- even though she couldn't be with him, she did love him, obviously -- this person that she loved is dying and so she gave him the Harun-El not quite knowing what the long-term effects of this are. As we find out, these long-term effects are really quite massive and quite all-encompassing. I think she has to deal with the fact that she made that choice for him and he didn't have a part of it and what that means for her and that responsibility. You know, it's very difficult to watch somebody going through something that they didn't have any part of and that you're responsible for. I think that is very difficult for Lena and you will see more of that ultimately as the full powers of the Harun-El and what is does become apparent.

What can you tease about that letter Eve left on Lena's desk?

I think that letter, when you read it, poses more questions than it ultimately answers.

Airing Sundays at 8 p.m. ET/PT on The CW, Supergirl stars Melissa Benoist as Kara Danvers, David Harewood as Martian Manhunter, Mehcad Brooks as Jimmy Olsen and Chyler Leigh as Alex Danvers.