|The Kryptonian Cure|
|Season 4, Episode 1|
|City On Fire||Brain On Fire|
The Kryptonian Cure is the first episode of Supergirl Season 4 and the 65th episode overall. It is the first part of the 8-part WAR OF THE SUPERMEN storyline.
A FATAL DEMONSTRATION- Lex Luthor and Lillian Luthor travel to D.C. to showcase D.I.S.C.O.R.D., the "golden girl" of Project Prometheus, as Dru-Zod formally declares war on Earth and humanity. At the DEO, Kara Danvers, Alex Danvers, Lena Luthor, and Maggie Danvers pick up the pieces from the havoc wreaked by the anti-Kryptonian terrorists.
- Melissa Benoist as Kara Danvers/Supergirl
- Chyler Leigh as Alex Danvers
- Jeremy Jordan as Winslow Schott
- Katie McGrath as Lena Luthor
- Laura Benanti as Astra In-Ze
- Tyler Hoechlin as Kal-El
- Zachary Quinto as General Dru-Zod
- Sarah Shahi as Ursa
- Odette Annable as Reign/Samantha Arias
- Jenna Dewan-Tatum as Lucy Lane/Superwoman
- Floriana Lima as Maggie Danvers
- Minka Kelly as Lois Lane
- Lauren German as President Veronica Banks
- Michael Rosenbaum as Lex Luthor
- Brenda Strong as Lillian Luthor
- Amy Acker as Brainiac
- Emma Tremblay as Ruby Arias
- Helen Slater as Eliza Danvers
- Katheryn Winnick as D.I.S.C.O.R.D.
- Chris Wood as M'On-El
- Amy Jackson as Imra Ardeen
- with Claire Holt as Karen Starr/Power Girl
- and Mechad Brooks as James Olsen/Guardian
Special Appearance By
- Calista Flockhart as Cat Grant
Special Guest Star
- Peter Facinelli as Max Lord
- Glenn Morshower as General Sam Lane
- Antagonists: Lex Luthor, D.I.S.C.O.R.D., Lucy Lane, Lillian Luthor
- Veronica was last seen in Sometimes. This is her first appearance outside of The Originals (tv series).
- This episode is Lex-centric, while the B-plot focuses on Zod, and the protagonists are given the C-plot.