Three pages from ACTION COMICS 5 and four from issue 6...
Remember, ACTION COMICS takes place at the beginning of Superman's career, so it's a time traveling Superman from the future in all the following scenes, working alongside the Legion of Superheroes.
The octopus is Erik Drekken (What, no snazzy codename, Morrison?), a villain with a pretty neat power. He's basically like Evolvo Lad from the Heroes of Lallor or Manikin from Alpha Flight, but to the nth power.
That leads into the scene that superfangirl posted, in which Superman searches his memory to find where it's wonky, in order to pinpoint the exact spot in his mind the bad guys are hiding.
Inside a tesseract in Superman's brain, the Legion successfully defeats the Anti-Superman Army and recover the kryptonite engine from them.