The casting shakeups in the Arrowverse continue as Chris Wood will not be returning for Supergirl season 4.

Note: This article spoils the events of the Supergirl season 3 finale. Proceed with caution.

Mon-El’s story reached its endpoint in the Supergirl season 3 finale, “Battles Lost and Won,” at least as far as his time in the 21st century is concerned. While he initially seemed ready to stay behind in 2018 to be with Kara again — he and Imra even break up — Brainy provides some news about the future that he can’t turn his back on.

Though the victims of The Blight were saved when Pestilence died, her death left a window open for other issues, such as the potential extinction of AIs in the future. Brainy was no longer safe so returned to 2018 where he would be safe. And he determined that the future needed both Mon-El and Winn.

Mon-El, having become a hero, could not turn his back on the future and the Legion. Kara is very understanding of this, telling him that his inability to do so is why she admires the man he has become. And thus, Mon-El returns to the future alongside Winn.

Related: Supergirl shakeup: Jeremy Jordan to recur, Jesse Rath promoted to series regular

“The plan for Chris was always to have him on the show for two years,” executive producer Robert Rovner tells TVLine. “We’ve loved telling Mon-El’s story, as well as the story we’ve told for him and Kara. We hope the fans felt that it was a satisfying conclusion.”

“They both have destinies in different times as heroes. What they did was the sort-of Casablanca decision of putting what’s most important to them — which is saving the world — first,” EP Jessica Queller adds.

“It’s a little bittersweet that one destiny is to be a hero in this time and one’s destiny is to run the Legion in another time, but I think they grew a lot from knowing one another. They have respect for one another, and they have a respect for the decisions they respectively made.”

However, the EPs are leaving the door open to Wood returning “if the story takes us there and if Chris is available.”