'Supergirl's Odette Annable on Her Onscreen and Offscreen Relationship With Sam's Daughter, Emma Tremblay

Tonight's episode of Supergirl will see another evolution in Reign, the season's big bad, as she teams with the first of her fellow Worldkillers for the first time. It's a major step forward for Reign, but one of which Sam -- her alter-ego -- is going to be unaware of.

Odette Annable, who plays both "halves" of the character, spoke with ComicBook.com about the thing that seems to complicate Reign's plans for world domination the most: Sam's daughter, Ruby, played by Psych: The Movie's Emma Tremblay.

"Sam, right now, she has no idea that she's Reign, so she's going through a real transformation," Annable explained. "She's taken care of her daughter since she was very, very young, on her own. She's always protected her, and they've built this wonderful friendship. Right now, I think, Sam is dealing with an overwhelming amount of guilt because she's sort of drowning. I think she's trying to make everything work, and she knows that she's disappointing her daughter, and she's disappointing work, and she's disappointing herself. She's also trying to raise a teenager, and trying to figure out why she's blacking out and losing time. I think, all of those things really play into where this arc is going, and when it's finally gonna blow up, and what's gonna happen with Sam and Ruby. That's coming, and I'm excited for everybody to see that."

The relationship between the two is full of intense scenes, and while Ruby has not yet met Reign, there have been a few scenes where Annable had to really yell at Tremblay -- not in a "harsh parenting" way but as her character was struggling with larger-than-life issues that were making her a bit less-than-stable.

"I was worried about it when I was first told about my arc, and where this was going. I wasn't able to chemistry test with anybody, so with Emma, I met her the first day on set," Annable said. "It just really worked out in the best possible way because she just has this maturity about her, and this way about her. She's just so beyond her years, and she's such an incredible actress. The way that she's able to just has this deep emotion that she wears on her sleeve, and it works so well for this character....I can't even explain it properly because she's just has so many layers to her, and I'm so grateful that we have a friendship off screen because it makes it so much easier."

"And, I'll tell you what, she's also great at improv, and that's not easy when you are 13, and when you're thrown stuff at you," Annable added. "We just have so much fun on screen. We just go back and forth. That's what sort of makes these characters so great, because it feels very real."

Supergirl airs Monday nights at 8 p.m. ET/PT on The CW. After tonight's episode, the series will take a 9-week hiatus until its return on April 16.