A split cover for Action 339 (July 1966), as the Superman of 2966 faces Muto, in a story by Hamilton, Swan and Klein, while Supergirl is caged by Brainiac, thanks to Jim Shooter and Jim Mooney.
The Superman of 2966 escapes from Muto’s trap, using the androids to bring him to safety. He has to struggle to deal with Muto, who keeps his base in the toxic waters.
Muto makes use of an enlarging ray. His plans are never very precise, but the art is fun.
It really looks like Superman is killing Muto, not just sending him back to his home dimension. But Muto does return, along with this Superman, in World’s Finest Comics the following year.
Sueprgirl has her first solo outing against Brainiac in this story. Superman leaves Earth in her care as he goes into space with the Justice League of America.
Brainiac has a trap all specially prepared for Superman, and comes to challenge him. He refuses to take Sueprgirl seriously.
But Supergirl will not give up, and keeps attacking over and over. Finally, Brainiac considers her enough of a nuisance to use his special kryptonite cage on her.
But the cage was built for Superman’s size, and Supergirl slips through the bars. It’s painful, but possible, and she defeats the unwary Brainiac and sends him running.