Action Comics 339, Jul 1966 comics.org
Shooter's Credit: writer
Story Title: Braniac's Blitz
Publisher: DC
Reading Status: required
Script: Jim Shooter
Pencils: Jim Mooney
Inks: Jim Mooney
Colors: unknown
Letters: unknown
Synopsis: Supergirl defends Metropolis from Brainiac while Superman is away on a space mission with the Justice League.
Characters: Superman, Supergirl, Brainiac, Professor Carter
Places: Metropolis, Stanhope College
Things: Green Kryptonite
Cliffhanger: Supergirl is trapped in a green kryptonite cage and Brainiac blasts her with a lethal force-shield ray.
Conclusion: The cage was made for Superman, so Supergirl was able to squeeze through the bars before the force-shield ray hit. Brainiac escapes by shooting himself with a time-travel gun.
Notes: Shooter's writing credit obtained from reprint in Superman Family 164.