Synopsis
Many years ago, one of Tony Stark’s closest friends – Connor "Rebel" O’Reilly – was accidentally killed during a trial run of Stark’s experimental Prometheus armor. This incident turns Stark into a shallow individual obsessed with money. Years later he is tried and acquitted for corporate espionage and insider trading. Much of the credit goes to the testimony of Dr. Leonard Samson – noted psychiatrist – and Jennifer Walters, his high-priced attorney. Neither are particularly happy about his acquittal.
During a party following the verdict, Pepper Potts publicly confronts Stark about his behavior. Their interaction is capped off with Pepper throwing a drink in his face. She is soon fired. Elsewhere Liz Ross - head of security at Stark International - receives a message that there is trouble at the Buffalo annex. She and Bruce Banner - one of Tony's employees - leave to investigate. Once they arrive, Banner knocks her unconscious and is revealed to be working with the terrorist group known as Hydra.
Banner is overcome with guilt at creating the gamma bomb for the military through Stark International. He naively believes that the terrorist group Hydra will help him dismantle the bomb. He soon finds out that Hydra is more interested in detonating it than dismantling it. When he tries to stop him, he in rendered unconscious as well.
Hydra locks him inside the test chamber, disable all the fail-safes, and begin the countdown. Both Ross and Banner awaken and realize that they can't stop the bomb. Banner realizes the grim situation he has created and has only one option remaining. Despite Betty's pleas, Banner lowers the chamber into a silo that runs 13 miles toward the center of the earth. He hopes that 13 miles of rock will absorb the excess gamma radiation and save an estimated 12 million people on the eastern seaboard. After he descends the silo doors are closed. Moments later the gamma bomb detonates.
Stark is eventually informed of the activity at the annex and decides to investigate. Jasper Sitwell - government liason to S.I. tries to talk him out of it, but can't change his mind. Pepper's comments have caused him to reflect on his behavior and he decides to take a more active role in his company. Stark arrives in Buffalo by helicopter to investigate and discovers a large crater 10 miles from the facility. When they arrive they discover a massive green-skinned creature roaming around the plant. The "hulking mass of gamma radiation" throws a giant boulder at the helicopter, causing it to crash. The Hulk then begins to search for his missing "friend".
Stark and Sitwell survive the crash, but the pilot does not. Sitwell states that he's near death and Stark has more pressing concerns pointing out the shrapnel embedded in Stark's abdomen. Stark wanders into the plant that he shut down years ago to hopefully find a way to save his life. He reminds himself why he closed the plant in the first place - this was where Rebel died. He then makes his way toward the Promethus armor – which is part mobile life support system – to stay alive.
Elsewhere Hulk has found Liz Ross and is trying to comfort her. Jasper Sitwell - whose intentionally deceived Stark about his condition - finds them and watches from a distance. He then watches as the Hulk is introduced to the newly reactivated Promethus armor, unaware that Stark is inside it.