Kara and Mon-El are on their mission in space, and J'onn is increasingly worried about Reign's immunity to Lena's sythnethtic Kryptonite.
Alex takes Ruby for ice cream, and someone starts shooting at them.
Kara and Mon-El arrive on another planet and try to blend in. Alex takes Ruby to the DEO and asks Winn to help her figure out who is trying to kill her.
Kara and Mon-El suprisingly run into Alura, and discover some from Krypton survived. Kara tells her they are searching for the rock to defeat Reign. Alura agrees to get the council together to decide on the black rock, but in the mean time, she wants to get to know her daughter.
Alex tracks down her first arrest, but he's not the one trying to kill her. She finds a bomb on her bike and gets away before it explodes.
Lena worries about what she should do if Supergirl doesn't come back in time. She could overload Reign with Kryptonite, but that would also kill Sam.
Kara pleads with the council of Argo for the black rock, and they agree to give her what she needs.
Alex and J'onn set a trap to catch the man trying to kill her. She chases him down and arrests him.
Alex questions whether her dangerous job will get in the way of her desire to be a mother someday.
Supergirl arrives just as Reign is about to escape.