Supergirl season 3
Kara and Alex Danvers in The CW series, Supergirl The CW/ DC TV

We have seen Supergirl fighting crime and saving the planet from alien invasion, but the upcoming episode of Supergirl season 3 will feature Kara Danvers' origin story in flashback scenes and explore her sisterly bond with Alex.

In episode 6 titled, Midvale, Kara (played by Melissa Benoist) and Alex (played by Chyler Leigh) take a road trip to Midvale for a break after the Department of Extranormal Operations (DEO) agent called off Alex's engagement with Maggie. Actress Izabela Vidovic plays young Kara and Olivia Nikkanen plays young Alex in flashbacks.

The official synopsis of the chapter airing on 13 November at 8pm EST on The CW Network reads as follows:

Kara (Melissa Benoist) and Alex (Chyler Leigh) head home to Midvale for a little R&R. While there, Kara recalls a painful memory of a childhood friend's death and how that traumatic experience brought the Danver sisters closer together

The promo shows the Danvers sisters taking a road trip home and reminiscing about their younger years. "I remember thinking I would never feel at home on Earth. But I feel at home with you," Kara says.

Alex responds to her sister's words and adds, "You and I can get through anything together."

In the previous episode titled, Damage, Alex ended her engagement with Maggie after realising that she wants to be a mother someday, but Maggie remained opposed to the idea.

Actress Chyler Leigh spoke to Den Of Geek about Maggie and Alex's heartbreaking split.

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"Alex would never wish anything but the absolute best for Maggie and vice versa. That's really where, I think, you kind of see what is most heartbreaking about the ending of their relationship is how much they love each other and how much they want the best for each other," she told the outlet.

"It's like you really see that the intention there is to allow them to be their best selves no matter what. I feel like we did a really good job with that," she added of the love story.

Click here to watch The Flash season 3 episode 3 live via The CW app. You can also watch the episode online by clicking here (only in the US).