'Supergirl' Reveals Ties Between Lex Luthor and Red Daughter in "The House of L" Preview

Lex Luthor came to National City in tonight's episode of Supergirl, but the iconic villain's influence goes a lot further than that. The CW has released a preview for next week's episode, "The House of L" and it looks like the series will finally be delivering on the highly-anticipated Red Daughter storyline -- and Lex Luthor is a key part of it.

In the preview, which you can check out in the video above, Lex has a secret weapon he intends to use to destroy Supergirl -- another Supergirl, the one currently training in Kasnia.

At the end of the season three finale, Supergirl used a Legion of Super-Heroes ring to travel back in time, after a battle with Reign (Odette Annable) turned surprisingly deadly. Once she'd traveled back in time, Kara separated Sam and Reign from each other, ultimately "killing" Reign. At the end of the episode, dark energy from the Harun-El was sent to Siberia, and seemingly produced an alternate version of Kara who arrived at a military base.

Producers confirmed shortly after it aired that they were planning an homage to Superman: Red Son, a popular alternative history story from the comics and while it's taken some time for the series to get to bring it to life this season, it's set to be a major storyline.

"A lot of our big storylines this season which we have been teasing out is the story of Red Daughter," executive producer Robert Rovner said at a recent Supergirl press event. "And so, in Episode 16, you get to see that Red Daughter's backstory does not only involve Red Daughter but involves Lex Luthor."

Jon Cryer, who plays Lex, teased that the storyline will see his character relating Supergirl -- or rather her Kasnian counterpart -- in a way that is very different than his usual rapport with Kryptonians.

"So, in some ways I am relating to Supergirl ... Kasnian version of Supergirl," Cryer said. "And it's fun, it's really fun to play with that relationship because it's so different. It's so different."

Supergirl airs Sundays at 8 p.m. ET on The CW. "The House of L" airs on March 24.