Supergirl finally learns the truth about Lena while tangling with Leviathan. J'onn J'onn makes a discovery about his brother's whereabouts.

Supergirl's struggle against Leviathan reaches a boiling point as she faces off against Rama Khan. Meanwhile, as Lena and Hope work to launch Project Non Nocere, Hope proves to be an invaluable asset to Lena.

The subsequent complications from the Crisis leave Supergirl to face a chaotic threat.

Supergirl helps Winn face his greatest fear. After Alex sets out to find evidence against Lex, Brainy must decide between helping his friend or continuing to secretly work for Lex.

Lex tasks Supergirl with protecting Andrea from an anti-tech extremist, but his nefarious purpose goes beyond merely keeping Andrea alive. Meanwhile, Lena moves forward with Non Nocere, with Lex’s help.

Lex proceeds to lay an intricate plan to bring Lena closer to him, defeat Leviathan’s latest attack, and pit Supergirl and team against Leviathan. It is also revealed how Lex came into power after Crisis.

Supergirl and the team go head to head against Rama Khan and Leviathan. Meanwhile, Lena and Lex must join forces when Project Non Nocere fails, leaving the two siblings in serious danger.

Supergirl realizes that in order to stop Lex and Leviathan she must work with the one person she never thought she’d trust again – Lena. Nia keeps dreaming about Brainy but struggles with what the dreams are trying to tell her. Meanwhile, Brainy realizes there is only one way to stop Lex.

As Brainiac lays close to death after trying to stop Lex, Supergirl and team soar in to save him, engaging in an epic battle with Gamemnae. After beating Leviathan, Supergirl turns her attention to Lex who has used the Obsidian platform to brainwash half the world to love him and follow him at all costs, no matter what horrible things he does. Knowing how dangerous this makes her brother, Lena enlists the entire team – Alex, J’onn , Dreamer, Kelly and Brainiac – to help, but Supergirl realizes that the only way to truly stop Lex is to sacrifice herself.