I don't know why there are a dozen long-clitted red roses on Kara's chest, I just know that there are. Alex, Winn, and James find her like this and evacuate her to the DEO. The DEO can't figure out what it is or why it has put Kara in a coma, and when they try to pull it off of her, it starts to kill her.
The first suspect here is Max Lord (obvs), but he claims not to know anything about it. We then see Non and Astra talking about a master plan they have called Myriad, which involves a solar storm and taking Supergirl down. So, the good news is that Astra is back. The bad news is that the rose-thingy is Non's doing and it's called a Black Mercy, which sounds horrific.
|Astra and Non revealing their master plan|
|I do not reject this fantasy|
Once she wakes up, Supergirl then goes after Non, while Alex and J'onn go after Astra. Just as Astra is about to kill J'onn, Alex stabs Astra through the heart with kryponite (nooooooo!). Supergirl gets to Astra just before Astra dies. Seeing that Supergirl is upset, J'onn tells her that he, rather than Alex, was the one who killed Astra (blub). He tells Alex later that he didn't want Supergirl to stop seeing Alex as her hero (double blub). And now, there's this angsty secret between the sisters.
Deep Thought of the Week: For Buffy fans, this episode might have reminded you of the episode "Normal Again." There, Buffy was stung by a demon that made her believe her life as a slayer wasn't real and that she was actually a patient in a psychiatric hospital.
A recurring theme in Buffy was that life on Earth was hellish (remember "Bargaining" in Season Six, after her friends brought her back from the dead, she asked, "Is this hell?"). In "Normal Again," it was in Buffy remembering her ties to her friends - her chosen family - that drew her out of the comforts of escapism and back to reality, however hellish it was. We saw a similar theme with today's Supergirl episode.