In the recent episode of Supergirl, Zod has put Supergirl in a coma via alien plant known as the black mercy to the dismay of Astra. Thanks to 2 guys from Cat Co Supergirl has managed to break free of the dream like world of Krypton that had never died. This leads to the death of Astra by Krytonite dagger used by Alex.
Martian Manhunter takes the fall for it to protect Alex from feeling guilty that she had offed a Kryptonian, not Supergirl herself. Zod vows revenge for the demise of Astra.
Supergirl resumes Mondays at 8pm on CBS.