Rhea used silver Kryptonite to control Superman. He sees General Zod instead of Kara. They fight an epic battle in the middle of National City until Kara manages to knock him out. 

Kara wakes up in the Fortress of Solitude with Alex and Kal-El. He's back to normal. 

Lillian gives Lena a device created by Lex to kill Superman that she adapt to use against Rhea. 

Kara invokes a sacred oath of Daxam to challenge Rhea to a duel. If Kara wins, Rhea will have to leave in peace. 

J'onn is still in a coma. He dreams of M'gann who urges him to wake up. He does. 

Clark and Kara talk to Cat about toning down the press. Supergirl doesn't want any innocent bystanders getting hurt. 

Lena figures out how to use the device to radiate the atmosphere with lead, meaning Mon-El would have to leave Earth. They plan on the device as a fail safe is Kara can't defeat Rhea. 

Kara fights Rhea, who brings in ships to destroy the city. Kara sends Mon-El to stop them. J'onn and Superman help too. 

Rhea bleeds Kryptonite, and Kara weakens. 

M'gann returns with other White Martians as back up. 

Kara sees no other choice than to use Lena's device. The Daxamites are forced to leave, but Rhea dies. 

Kara and Mon-El share a tearful goodbye before Mon-El is forced to get in the pod and leave. 

Kal tells Kara that she's so much stronger than he is. 

Alex proposes to Maggie. 

Cat secretly knows Kara is Supergirl. 

35 years ago, the day Krypton died, another baby is sent off in a pod.