Brainstorm was an under-utilized Justice League villain, who had not appeared in ten years when Bates, Swan and Blaisdel resurrected him for Superman 294 (Dec. 75).
The story begins as Clark Kane tapes a newscast, relating how everyone on Earth vanished. As Superman believes he will be able to solve whatever caused this, he sets up an explanation as to how both he and Clark Kent were off planet at the time.
Brainstorm lures Superman by pretending that he has killed Clark Kent. Obviously, Superman does not fall for this, but he goes anyway, to understand just how Brainstorm pulled off getting rid of everyone. It turns out he simply dreamed them away – which means he must have been wearing his big thinking cap helmet while sleeping, as that is what amplifies his powers.
Playing off Brainstorm’s own lie about killing Clark, Superman gets back into that identity. Brainstorm’s mental blasts are intended to kill a human, so they fail to affect Clark. Although he potentially exposes his identity in capturing Brainstorm, as he suspected, the villain simply believes that Superman disguised himself as Clark.
It’s actually one of Brainstorm’s better stories, which says a lot.
It’s also Brainstorm’s one and only appearance in the 1970s. He returns in the early 80s in Superman Family.