With the three other Arrowverse shows now over for the season, it's only Supergirl left. This episode was an interesting one. Here's what happened:
Supergirl 3x20 "Dark Side Of The Moon"
We start with Mon-El and Kara in space looking for the Rock Of Yuda Kal. But their coordinates take them to something a little unexpected: a floating city, trapped in a dome on a chunk of rock. Mon-El and Kara's ship is pulled in, and soon after they wander off they're attacked by robots. They steal cloaks to blend in and keep exploring. Eventually they come across a little landmark and Kara recognizes the text on it as Kryptonian, making her realize that this little floating city is actually Argo and is the last bit of Krypton that somehow managed to survive. Her realization is further confirmed when a group of Kryptonians approach them, and one of them is Alura herself. Kara is thrilled to be reunited with her mother. Alura explains that saving Argo was a shot in the dark that they didn't think would work (hence why little Kara and baby Kal were shipped off) and the city's continuous survival is a fickle thing, so Alura is reluctant to promise Kara help with Reign. But she does take Kara to see a council of leaders so Kara can plead her case. Kara tells them of Earth's fight against Reign and how desperate they are for that Rock. The council votes and ends up agreeing to give it to her. Mon-El, meanwhile, goes to return the cloaks he and Kara borrowed, and in return for them, gives a little sick kid futuristic medicine to help his disease that Argo can't rid itself of due to the city's ecosystem. With the Rock Of Yuda Kal in hand, Kara and Mon-El head back to Earth.
And over on Earth, Alex is still on Ruby duty, but things go awry when Alex is attacked. A man tries to shoot her and then throws a grenade. Luckily, Alex manages to evade death, but she's still worried not only for herself but for Ruby. She takes Ruby to the DEO so Winn can take over babysitting while Alex and J'onn try to figure out who the attacker is. At first Alex thinks it's the guy she arrested as a teenager (from that wonderful flashback episode) but she finds him in a bar and he denies it. And then Alex's motorcycle is blown up. So their new plan is for J'onn, disguised as Alex, to pretend to go for a jog while the real Alex and several armed DEO agents keep watch from around. But J'onn isn't attacked, the real Alex is, and so Alex chases after the guy. With the help of Winn's special suit, she's able to climb, jump, and move with super-esque ease, and it's cool to watch, even if Alex pushes herself almost too far when she makes a few rather dangerous jumps and is almost shot. But she manages to do this crazy flip and grab his gun from him. She gets him on the ground as he admits that he's an alien (which is how he know J'onn was a fake Alex).
As for Winn, he doesn't take too easily to babysitting (which confuses me - isn't he just a big kid himself?) because he's stressed and tired, but soon he warms up to Ruby when he realises that they both have an evil parent.
And that leaves Lena, who is struggling to contain Reign. She keeps upping the kryptonite intake, but it's a temporary solution, and Lena is worried that eventually she'll have to choose between saving Sam or saving the world.
Though Alex's attacker has been caught, she is still worried. She's worried about how she throws herself into her dangerous work, and how that isn't good if she wants to not only look after Ruby but also have a child of her own one day. J'onn assures her she'll figure it all out, but Alex isn't sure. Will Alex leave the DEO? What will she do then? Can the DEO handle losing their best agent?
The last scene is of one of Argo's leaders, the one who looked a little surprised at Kara's presence, donning a dark cloak and communicating telepathically with Reign, who is up and taunting Lena again. Mon-El and Kara return to the DEO with the Rock Of Yuda Kal just as she breaks out of her special cell.
All in all, a decent episode. Nothing too special. I mean, I always like Erica Durance on the show, but that's because I miss her as Lois Lane more. Learning about Argo was cool but I feel like it's too late in the season to really make it a big deal, which it should be. Also, why couldn't that hologram of Alura have told Kara that she's alive? Or even that they had this slim backup plan?