The fact that Chris Wood would be returning to Supergirl this season has been known since San Diego Comic-Con 2017 — but just what the fate of Mon-El would be has been slowly trickling in with casting announcements for members of the Legion of Super-Heroes. But the trailer for next week's episode shows us that the Kara/Mon-El reunion will take place soon, and it's likely tied to the alien ship in the water near National City.
Supergirl (Melissa Benoist) laced the sky with traces of lead, which would be poisonous to Daxamites and a way to stop the alien invasion — but Mon-El, the Daxamite Prince, was also affected and had to leave the planet. He ended up in some kind of wormhole, which was the end of Season 2. Along with Mon-El's return, we'll meet Saturn Girl (Amy Jackson) on Monday and then Brainiac 5 (Jesse Rath) in an episode aptly called Legion of Super-Heroes.
Benoist talked about Mon-El's return with EW.com:
"It's going to be weird and difficult. You watch Castaway, and Tom Hanks returns and Helen Hunt doesn't know what to do."
But this Mon-El is different in more ways than just he can survive on Earth, even with the lead in the air. Benoist talked about how it would be difficult for Kara just to pick up where they left off after what she'd gone through the last few months.
"He was the first love that she's ever had. I know they had their differences up until the end, but toward the end, they really saw each other on an even playing field. They were peers. She said, 'Go be a hero, you're ready.' They believed in each other, so losing that confidante, that support, that love was devastating to her. I feel like, for the first time, especially since we've started the show, she really felt like she had it balanced — she had a happy life with her partner, she had work going for her and was working her way up in the premiere, and she was loving being Supergirl and saving the world, so a giant part of her identity was wrenched from her."
Supergirl airs Mondays at 8 p.m. ET on the CW.