Supergirl's Darkest Day! is a Supergirl story appearing in Action Comics #263.


After Supergirl rescues a boy from drowning in the ocean, the boy gets taken to the Midvale Orphanage. There, under the name of "Johnny Blank", he begins learning English from Linda Lee, who has volunteered to be his tutor. However, he quickly reveals he's aware of her secret identity!

Supergirl soon deduces the boy is an alien, and tells him. He confirms that his real name is Valzorr, from the planet Korvia. Coming from the royal family of his world, his ship crashed on Earth. However, he can't return home lest he face the death penalty for murder of the King and Queen. Supergirl takes him home and proves his innocence.