Conway, Estrada and Wood conclude the first storyline in All-Star Comics 59 (March/April 1976).
While the heroes of the Justice Society and Super Squad deal with the situations he has created, Brainwave occupies his time by beating up illusions he has created of them. A decrepit old man shows up, who Brainwave has been eagerly awaiting.
The story then picks up on the three sup groupings. Flash and Wildcat bring Power Girl to the JSA headquarters. Wildcat thinks she should not be allowed in. Frankly, at this point I wouldn't trust her either, as she has not really explained why she knows Brainwave is the villain, or is aware of his location. But the Flash trusts her, and they take the Society's acorn shaped rocket out into space, to Brainwave's lair.
In each case it is the Super Squad member who gets to shine. Robin figures out that the gas explosions are really just illusions, while neither Green Lantern nor Dr. Fate were able to deduce that.
And it's the Star-Spangled Kid who stops the earthquake, while Hawkman and Dr. Mid-Nite are busy battling Brainwave's men.
Up in his satellite, we learn that Brainwave has been draining the powers of the heroes and channelling them into a machine which he uses on the old man, who proves to be Per Degaton, another old Society foe not seen since 1947. Degaton gets a new body, which really doesn't look much like his old one, but does very little in the tale. The three groups all converge on the satellite and begin fighting the two villains.
And, of course, it is the Super Squad members who get to shine, and defeat Brainwave. Power Girl leads Green Lantern in stopping his plan to send the Earth hurtling into the sun.
So as the story ends the Society decide to make the Super Squad members part of the JSA. Of course, Robin already was one, anyway. And for that matter, Robin then stops appearing for a while, only showing up in the next JLA/JSA crossover.
The interplay between Wildcat and Power Girl is really the best thing in this new run.
Brainwave returns in this book the following year, but Per Degaton is not seen again until 1985, in the America vs the Justice Society miniseries.