The plot of the series follows a framework story line in which the U. S. government passes a Superhero Registration Act, ostensibly designed to have super powered individuals act under official regulation, somewhat akin to law enforcement. However, superheroes opposed to the act, led by Captain America, find themselves in conflict with those supporting the act, led by Iron Man, with Spider-Man caught in the middle; the X-Men take a neutral stance. The superheroes in support of the law, such as Iron Man, Mister Fantastic and Ms. Marvel, become increasingly authoritarian. In the aftermath of the war, Captain America surrenders and is imprisoned. The conflict between freedom and security is an underlying theme in the story line, with real-life events and discussions, such as the U. S. government's increased surveillance of its citizens, serving as a backdrop for the events in Civil War. A sequel, Civil War II, debuted in June 2016.