The following contains spoilers for She-Hulk #8, on sale now from Marvel Comics.
She-Hulk reveals the origin of April and Mark Booth, two married scientists whose experiments and lust for power came with disastrous side effects.
The couple made their first appearance in She-Hulk #4, Mark shown as a hulkish figure with a limited vocabulary and April a small woman with an oversized head. Written by Rainbow Rowell and illustrated by Takeshi Miyazawa, She-Hulk #8 focuses entirely on Mark and April, telling the story of how they went from ordinary scientists to the transformed beings they are now. Much like the original Hulk, Bruce Banner, their metamorphosis resulted from a Gamma radiation project gone wrong.
As the issue explains, Mark and April met while working together for April's startup company, Booth Cybernetics, and fell in love partially because Mark "believed [April] was capable of anything" and "could have whatever she wanted." Since "April wanted power," the two began to investigate ways they could become superhuman, settling on using Gamma radiation to become Hulks. Because Jennifer Walters became She-Hulk following a blood transfusion given by her cousin Bruce, the two take in Jen's blood intravenously together.
Though they turn into green hulks for a second, Mark becomes more monstrous and rageful, while April's head grows massive and her intellect increases, the two now similar to Banner and Hulk villain the Leader, respectively. Mark uncontrollably turns into and out of his Hulk form as a result of his emotions, but over time, he regresses, his intelligence dwindling as he remains in his Hulk form more often. To control Mark's outbursts, he puts on wrist and ankle restraints that April can use to force him still when necessary.
She-Hulk's New Enemies May Be Behind Jack of Heart's Return
At the end of the prior She-Hulk #7, April and Mark captured Jen and trapped her in their basement laboratory, which features a damaged capsule much like the one that Jack of Hearts broke out of following his apparent resurrection. It seems that April and Mark are responsible for bringing Jack back to life, a hero who once accidentally drained Jen of her Gamma radiation, but no longer possesses this power. In She-Hulk #8, April discusses moving and draining radiation to Mark, and she is last seen staring at photos and notes of She-Hulk while the issue's narration says, "You could take her radiation...someone had before."
Along with Rowell and Miyazawa, She-Hulk #8 is colored by Rico Renzi and lettered by VC's Joe Caramagna. Main cover art for the issue is illustrated by Jen Bartel, with variant cover artwork contributed to by Michael Dowling, Morry Hollowell and NetEase. The issue is now on sale from Marvel Comics.