CBR

In Superman #156, Superman was apparently dying of a Kryptonian disease. 1 / 8

Supergirl traveled back in time to Krypton to find a cure, but failed. 2 / 8

The virus turned out to be bogus and Superman lived. 3 / 8

However, how did Supergirl return from past Krypton? It was under a red sun! 4 / 8

Future Mort Weisinger assistant editor, E. Nelson Bridwell, writes in with a clever answer. 5 / 8

He referenced Superboy #81, where Superboy lost all of his powers. 6 / 8

He was on a world with a higher gravity and a red sun. 7 / 8

Then red kyptonite cured him. And he presumably gave some to Supergirl. 8 / 8