Kara (Melissa Benoist) will come face-to-face with her Aunt Astra (Laura Benanti) and it will be anything but a peaceful reunion in the upcoming episode of the CBS series "Supergirl."

After the revelation by Vartox (Owain Yeoman), viewers now know that the person who really wants to kill Kara is her mother's twin sister. She sent the villain to National City to cause chaos and ultimately finish off her niece. Alura, Kara's mother, imprisoned Astra at Fort Rozz along with the other Kryptonian bad guys. While it has yet to be revealed what Astra did to merit being imprisoned for a long time, the female general has since harbored intense feeling of hate for her blood relatives.

During their October interview with The Hollywood Reporter, executive producers Andrew Kreisberg and Greg Berlanti talked about the time they came up with the plot pitting Supergirl with a family member. According to Kreisberg, they especially loved that the hero and the villain were linked by blood, which made their fight a lot more personal. The fact that Astra was the exact replica of Supergirl's mother Alura made it even cooler. Fighting her aunt would reportedly have an emotional impact on Kara, and that it would be one of her biggest obstacles to overcome.

"Every time she punches her aunt, she's really punching her mother. And how much of her mother might still be inside her aunt is something we're going to be looking at as the series progresses," Berlanti said.

Meanwhile, Benanti revealed to TV Line what has been going on in her character's mind as she prepared to kill Kara. According to her, while Astra had been locked away on the Kryptonian maximum-security prison, she had a lot of time to hate her sister. Making Kara, being Alura's daughter, suffer would be the next best thing for her revenge. The actress also disclosed a surprising revelation about Astra and her mission on Earth. Aside from getting payback, she's in the planet to protect it from harm.

"She is single-minded in her focus of what she has been sent to Earth to do, and she's not going to allow anyone to get in her way of doing that — not even her niece, not even her family," Benanti said.

"Supergirl" airs Mondays at 8 p.m. EST on CBS.