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.