The Avengers, led by Captain America, find themselves involved in a devastating incident of international caliber. The government decides to implement a Mutant Registration Act to control all people with special powers. Steve Rogers sees this agreement as a violation of civil rights and openly rebels against the new regime, leading a group of mutants that support him. In his turn, Tony Start believes the agreement is reasonable and heads those who think the same. All this leads to the split of the Avengers and war. Fighting with each other, Start and Rogers do not realize that a mysterious Baron Zemo is already building his plant taking advantage of the split.