Sunday’s episode of “Batwoman” provided major insight for Rachel Skarsten’s Alice on exactly how she became a killer. The CW's newest superhero drama also showed the vulnerable side of the Gotham City tormenter.

“That was probably the most challenging episode that I’ve done so far on the show but definitely one of the most rewarding and cathartic,” Skarsten told International Business Times. (Spoiler alert! Do not read further before watching the March 16 episode.)

“Batwoman” Season 1, episode 15 revealed that while held in captivity, Cartwright’s mother (AKA The Queen of Hearts) started wearing Alice’s mother’s earrings. After some poking around, Alice found her dead mother’s head in Cartwright’s freezer (he intended to give his mother the face), and that’s when she killed her first victim, Cartwright’s abusive mother. After learning this, Kate strangles an already-injured Cartwright. She tries to revive him, but he's dead. Alice offers to help bury the body.

Skarsten told IBT all about the emotional episode and what Kate killing someone means for the Kane sisters moving forward.

IBT: How was this episode for you getting to play Alice being so vulnerable?

Skarsten: I think at the beginning everyone kept saying to me, ‘Oh is it really hard to play this super dark character? Does that affect you?’ And I was like, ‘No! What are you talking about?’ [Laughs] Cut to me writhing on the floor. I was like, ‘Yeah, this is definitely tough.’ But I also was so excited for it because to me what makes the crazy killer that is Alice lovable is really getting to see what made her into that and all the vulnerabilities and all the brokenness, and so any opportunity that Caroline [Dries, showrunner] gives me to play that is so welcome.

IBT: I love that this is another flashback episode. Did you know the information that was in this episode ahead of time or were you learning as you read the script?

Skarsten: Caroline did give me a heads up for this episode, however, just because of how emotionally taxing it was gonna be, and to sort of prepare myself for that, which I did appreciate. So I had a little bit of warning about what was gonna happen, but not much ahead of filming the episode. So I haven’t known all of this from the birth of Alice at the beginning of the season.

How does her father coming to her rescue change things? Does that change how Alice views things or their relationship?

Skarsten: Yeah, I love her relationship with Jacob. I think in ways it’s an ultra-magnified version of many child and parent relationships because no parent is perfect nor is any child. It’s such a complex relationship, and I think for Alice, and I think this is true for everyone, when you have a real trauma or real betrayal by a parent, there’s a part of you that freezes in that moment. And there’s a lot of anger and a lot of distrust, but at the same time, they’re still your parent and you still love them and you still want them to come through for you….

There’s a moment in this episode where they’re together and he saved her and it’s so beautiful. It’s as though Alice is back to being 13-year-old Beth again, and I just loved how it was written. I think their relationship sort of sums up Alice on a whole: the hope for redemption but the inability to get there most of the time. I think they both very much want to go back to a time that neither of them are quite capable of getting to, but you see them try all the time.

Plus, I really love Dougray [Scott, who plays Jacob Kane], so it’s quite lovely to work with him. I’m always like ‘Write me more scenes with Father please.’ [laughs]

Batwoman Rachel Skarsten
Rachel Skarsten is pictured in character as Alice in "Batwoman" Season 1, episode 15. Shane Harvey/The CW

IBT: Kate does kill Cartwright in this episode and Alice doesn’t seem mad about it. Is she happy? Does this kind of put Kate on her level?

Skarsten: Oh, of course. I think there’s a bit of jealousy that exists on the part of Alice because Kate sits up on her high horse and does good. I think for Alice, first of all, she thinks she’s doing good. Also, she feels very justified in her actions because of the trauma that she’s been through.

I think getting Kate to a point where she also becomes a killer, for Alice, it’s this great justification and vindication because up until this point, Kate has said so many times, verbatim, ‘You can’t kill anyone, you can’t kill anyone.’ And yet, put in a similar situation, she’s no different than Alice, in Alice’s eyes. So I think it’s a wonderful, messed up victory for Alice for sure.

I don’t know if it was part of her plan from the beginning, but as things have evolved, I definitely think it was an integral part of her plan that she achieved.

IBT: Can you tease at all how this is going to change the sisters’ relationship moving forward?

Skarsten: I think it very much changes how they see themselves and each other through their own eyes. And we sort of go back and forth in that relationship between intense love and intense hate but in ways that leveled the playing field between the two of them.

I almost think that it probably affects Kate more than it does Alice because in Alice’s mind, this has always been a possibility. Had Kate been in that situation, she would’ve done the same thing. Anyone would’ve done the same thing that Alice had done, but I think Kate has held onto this belief that it could have been different.... And now we see, well, maybe she wouldn’t have. So I think that leads to very big changes in the dynamic of their relationship.

"Batwoman" airs Sundays at 8 p.m. EDT on The CW.

(This conversation has been edited for length and clarity.)