Incredible Hulk #169 (1973)

The Harpy has just defeated the Hulk, and as General Ross watches the news coverage on TV he rushes out to the scene of the battle, recognizing the Harpy as his daughter Betty. When he confronts his daughter he tries to talk her out of killing the Hulk. Thinking it's all a trick she flies away with the Hulk in her clutches. When the military sends out fighter jets to stop her she shoots one out of the sky before she and the Hulk are swept up in a strange tornado that sweeps them into a giant cloud mass. They soon find themselves on some strange city hidden in the clouds. As the Hulk revives they are confronted by a two-headed creature calling itself the Bi-Beast. When they grab the Harpy in interest she lashes out with Gamma ray blasts, and the Hulk, wanting to protect Betty attacks the creature as well. The Harpy is easily knocked out with a single blow, but the Hulk proves to be more of a challenge. However, despite the fight the Hulk puts up, the thin air in the upper-atmosphere is what does him in and he collapses from lack of oxygen and reverts back to Bruce Banner. When Banner revives he explains to the Bi-Beast that he is a scientist, leading the creature to believe that destiny has brought him to the floating island. The Bi-Beast explains that this island was created by the Bird People and the Bi-Beast was created to be a living monument of their achievements once they have passed on. They explain that the machines are starting to break down and they have no knowledge on how to repair them and ask that Banner figure out how to fix them. They also explain that they captured the Harpy because they yearned for the company of someone that resembled their creators. When Banner begins to consider a way to change Betty back to her human self, however when he goes to get her he finds that the Bi-Beast had put her in a cage. Bruce demands to have access to the Harpy otherwise he will not work for them and the creature agrees, sedating her and handing her over to him. Bruce then devises a machine to change her back to her human form. Things go from bad to worse when MODOK, searching for the Harpy, arrives and seeks to exploit the island. Learning what is going on, he tricks the Bi-Beast into believing that Bruce Banner is evil and the creature leads him to Banner and stops him from doing anything just as he activates the machine to change Betty back to normal. This works up Bruce enough to transform back into the Hulk and resume fighting the Bi-Beast. MODOK then betrays the Bi-Beast, claiming the island for AIM and deploying his troops and shooting the Hulk in the back, knocking him out. When the Bi-Beast tries to fight back MODOK and his forces open fire on the creature, delivering a killing bombardment of ray blasts. In his last effort, Bi-Beast sets the island to self-destruct sending MODOK and his minions fleeing for their lives. The Hulk has reverted back to Bruce Banner once more and goes to grab the now revived Harpy to try and find a way off the island. When a crumbling building falls on the Harpy, Bruce goes to her aid and when the dust clears he is relieved to find that she has transformed back into Betty Talbot again. Without the Harpy's wings to fly them to safety they brace themselves for the island's destruction, however, the ground beneath them breaks open sending them falling to the ground as the island explodes. While they have escaped being killed in the explosion the fall will surely see them to their doom.