"Supergirl" will be focusing heavily on the sisterly bond between Kara (Melissa Benoist) and Alex Danvers (Chyler Leigh). Not only will they be the center of the upcoming third season, the siblings will also be featured heavily in the Arrowverse crossover.

Executive producer Andrew Kreisberg told Entertainment Weekly that the Arrowverse crossover will showcase the relationship between Kara and Alex, which has always been one of the show's central themes.

"Kara and Alex are at the center of it through all four hours," Kreisberg said. "One of the things we've been doing a lot this season is getting back to season 1 and really making it Danvers sisters-centric, so a lot of what's going on this season is Kara and Alex doing things in tandem, and the crossover won't be any different."

Arrowverse crossovers usually see the stars of The CW shows "Supergirl," "The Flash," "Arrow" and "Legends of Tomorrow" coming together.

As for "Supergirl," season 3 episode 6 titled "Midvale" will heavily feature the Danvers sisters. The two will relive a murder mystery from their high school days when they pay their hometown a visit.

Benoist told Entertainment Weekly that the episode will show how a Kryptonite finds and builds a family with a human for a sister. This supports Supergirl's character arc this third season as the actress earlier revealed that they will be exploring Kara's identity.

Losing Mon-El (Chris Wood) at the end of season 2 brought a new kind of heartbreak to the superhero, which is why she will be dedicating her time to crime-fighting and discovering "whether she's human or an alien and which she wants to be," Benoist explained.

The CW has cast Olivia Nikkanen to play the young Alex and Izabela Vidovic as the young Kara.

"Supergirl" will return to The CW on Monday, Oct. 9 at 8 p.m. EDT. The Arrowverse crossover will be on Nov. 27 and 28.