The long-gestating "Red Daughter" subplot on this season of Supergirl will be moving much more quickly in the second half of the season, which begins tonight.

Executive producers Jessica Queller and Robert Rovner told ComicBook.com that this was one of a number of storylines that will dovetail as the season winds down, taking seemingly-disparate threads and revealing connections between them.

"It comes much faster when we come back," Rovner said of the Red Daughter plot. "But we did want to tease it out, so that we were able to platform Agent Liberty and some of the other stories that we were beginning in the first group of episodes. We didn't want the Red Daughter story to overshadow that, and we thought it was very intriguing to tease out her evolution. We will eventually get her origin story, but we wanted to tease it out that way."

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 Harunel 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.

Superman: Red Son was a three-issue Elseworlds story from Mark Millar, which had Superman's pod land in Soviet Russia thanks to a slight change in the Earth's rotation. The Kryptonian then grew up as Russia's greatest weapon, facing off against the Justice League and Lex Luthor. Fans have campaigned for the story to be adapted into animation or live-action, but no progress has been made yet.

It's unclear exactly how much of Red Son will play a role in the events of Season 4, especially with regards to Supergirl's established canon and timeline. To an extent, that final scene almost feels like a sort of amalgam of Red Son and "Supergirl: The Last Daughter of Krypton", a 2011 storyline that sees a memory-wiped Kara land in Siberia. So it's safe to assume that however Red Son comes to Supergirl, it will be done in a pretty unique manner.