|Sine Qua Non|
|Season 9, Episode 11|
|A Glimmer of Hope||Never Know|
- Melissa Benoist as Kara Danvers/Supergirl & Red Daughter
- Chyler Leigh as Alex Danvers
- Katie McGrath as Lena Luthor
- Odette Annable as Reign & Samantha Arias
- Olivia Wilde as Susannah Russo
- Tyler Hoechlin as Clark Kent/Superman
- Claire Holt as Karen Starr/Power Girl
- Adelaide Kane as Ava Blackwood (comatose)
- Minka Kelly as Dawn Granger/Dove
- Jenna Dewan as Lucy Lane
- Emmy Rossum as Zaora Dru-Zod
- with Laura Benanti as Astra In-Ze
- Mehcad Brooks as James Olsen/Guardian
- and David Harewood as J'onn J'onzz/Martian Manhunter
- Emmanuelle Chriqui as Sarah Essen
- Rachel Nichols as Slam Bradley
- Crystal Reed as Sofia Falcone
- Taylor Cole as Lady Liberty
- Meagan Rath as Onyx
- Jessica Rothe as Alexandra Luthor
- Andrea Brooks as Eve Teschmacher
- with Sam Witwer as Ben Lockwood
- and Matthew Fox as Graham Etchison
- Antagonists: Lady Liberty, Sofia Falcone
- Sine qua non is a Latin phrase referring to an essential action, condition, or ingredient.
- This episode takes place on April 20, 2024.
- This trilogy of episodes is James-centric.
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