The Avengers #86

"Brain-Child to the Dark Tower Came...!"

The Avengers and Nighthawk from the Squadron Supreme are rushing to Atomic City to stop members of the Squadron from launching the satellite Brain-Child One into space because it may well destroy the entire Earth.[1] The Avengers rush onto the scene, the Scarlet Witch using her powers to halt the launch which causes a brief battle with Hyperion, Dr. Spectrum, and the Whizzer before Nighthawk arrives to break up the fight.  When inquiring about who built the shuttle, Dr. Spectrum explains that it was created by a being named Brain-Child. The Brain-Child's parents were exposed to excessive amounts of radiation, that caused their child to have a great capacity for knowledge, and soon became the smartest being on the planet and was the mastermind behind the satellite that was supposed to defend the United States. Deciding that Brain-Child is a threat, the combined forces of the Avengers and the Squadron Supreme decide to stop the boy before he can attempt to destroy the Earth again.

Meanwhile, on the Avengers home reality, Thor and Black Panther seek the aid of Iron Man to help them locate their missing comrades, using the combined effort of Thor's hammer, and one of Tony Stark's machines.

While on the Squadron's Earth, the heroes attack the Brain-Child's citadel and find their attack countered by a bunch of creatures created by the Brain-Child's own mind. During the fight, Hyperion is knocked out, but Goliath uses him as an "arrow" to knock Brain-Child out of his control chair, causing his constructs to disappear. With the Brain-Child defeated, Dr. Spectrum uses his power spectrum to change the Brain-Child back into a normal boy.

Just as the Squadron and the Avengers claim victory, the Avengers have transported back to their own world thanks to Thor. There they explain their story to Thor and the Black Panther and leave to celebrate. The Vision stays behind to contemplate the idea of parallel worlds.