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.

Gemma Cooper, alias Gamemnae, incarica Rama Khan di procurare la Kryptonite custodita nel DEO.

Ora che Rama Khan e' in possesso della Kryptonite, Supergirl non puo' combattere ne' lui ne gli altri dominatori degli elementi.