With the world now aware of his dual life as the armored superhero Iron Man, billionaire inventor Tony Stark faces pressure from the government, the press and the public to share his technology with the military. Unwilling to let go of his invention, Stark, with Pepper Potts and James 'Rhodey' Rhodes at his side, must forge new alliances – and confront powerful enemies.

A representative of an alien race that went through drastic evolution to survive its own climate change, Klaatu comes to Earth to assess whether humanity can prevent the environmental damage they have inflicted on their own planet. When barred from speaking to the United Nations, he decides humankind shall be exterminated so the planet can survive.