At Culver University in Virginia, General Thaddeus "Thunderbolt" Ross meets with Dr. Bruce Banner, the colleague and boyfriend of his daughter Betty, regarding an experiment that Ross claims is meant to make humans immune to gamma radiation. The experiment—part of a World War II-era "super-soldier" program that Ross hopes to recreate—fails. The exposure to gamma radiation causes Banner to transform into the Hulk for brief periods of time, whenever his heart rate rises above 200 beats per minute. The Hulk destroys the lab and surrounding area, killing several people inside and injuring the General and Betty, and others outside. Banner becomes a fugitive from the U.S. military and Ross, who wants to weaponize the Hulk.

Five years later, Banner works at a bottling factory in Rocinha, Rio de Janeiro, Brazil, while searching for a cure for his condition. On the internet, he anonymously collaborates with a colleague known only as "Mr. Blue." He is learning Yoga techniques to help keep control and has not transformed in five months. After Banner cuts his finger, a drop of his blood falls into a bottle, which is eventually ingested by an elderly consumer in Milwaukee, Wisconsin, giving him gamma sickness. Using the bottle to track down Banner, Ross sends a special forces team, led by Emil Blonsky, to capture him. Banner transforms into the Hulk and defeats Blonsky's team. After Ross explains how Banner became the Hulk, Blonsky agrees to be injected with a small amount of a similar serum, which gives him enhanced speed, strength, agility, and healing and begins to deform his skeleton and impairs his judgment.

Banner returns to Culver University and reunites with Betty. Banner is attacked a second time by Ross and Blonsky's forces, tipped off by Betty's suspicious boyfriend Leonard Samson, causing Banner to again transform into the Hulk. The ensuing battle outside the university proves futile for Ross' forces, and they retreat, though Blonsky, whose sanity is faltering, attacks and mocks the Hulk. The Hulk severely injures Blonsky and flees with Betty. After the Hulk reverts to Banner, he and Betty go on the run, and Banner contacts Mr. Blue, who urges them to meet him in New York City. Mr. Blue is actually cellular biologist Dr. Samuel Sterns, who tells Banner he has developed a possible antidote to Banner's condition. After a successful test, he warns Banner that the antidote may only reverse each transformation. Sterns reveals he has synthesized Banner's blood samples, which Banner sent from Brazil, into a large supply, to apply its "limitless potential" to medicine. Fearful of the Hulk's power falling into the military's hands, Banner wishes to destroy the blood supply.

A recovered Blonsky joins Ross' forces for a third attempt to take Banner into custody. They succeed, and Banner and Betty are taken away in a helicopter. Blonsky stays behind and orders Sterns to inject him with Banner's blood, as he covets the Hulk's power. The experiment mutates Blonsky into the Abomination, a creature with size and strength surpassing that of the Hulk. He attacks Sterns, who gets some of Banner's blood in a cut on his forehead, causing him to begin mutating as well. The Abomination rampages through Harlem.

Realizing that the Hulk is the only one who can stop the Abomination, Banner convinces Ross to release him. He jumps from Ross' helicopter and transforms after hitting the ground. After a battle throughout Harlem, the Hulk defeats the Abomination by nearly strangling him to death with a chain, but spares his life upon hearing Betty's plea and leaves the Abomination for Ross and his forces to arrest. After having a peaceful moment with Betty, the Hulk flees New York.

A month later, Banner is in Bella Coola, British Columbia. Instead of suppressing his transformation, he begins to transform in a controlled manner with a slight smirk. Later, Tony Stark approaches Ross at a local bar and informs him that a team is being put together.
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Marvel Studios (usa)