Struggling with PTSD following the events in New York, Tony Stark is restless and haunted by the fear of failing to protect those he cares about. He has become obsessive about perfecting the Iron Man suits, much to the concern of Pepper Potts, his girlfriend and CEO of Stark Industries. Amidst his personal turmoil, the world faces a new threat from the Mandarin, a shadowy terrorist leader who orchestrates a series of bombings around the globe. Stark’s personal world suffers a devastating blow when his home is attacked and destroyed after he issues a public threat to the Mandarin, leaving him to rely on his intellect and instincts to protect those closest to him and to uncover the mystery behind the Mandarin.

Stark finds himself in rural Tennessee with a malfunctioning suit, cut off from his usual resources and allies. In his attempt to piece together the truth behind the Mandarin attacks, he teams up with a precocious young boy who helps him investigate the origins of the bombings. Meanwhile, Aldrich Killian, a scientist snubbed by Stark in the past, has emerged with an innovative and dangerous technology known as Extremis, which grants users superhuman abilities. Stark's pursuit of answers brings him into a web of intrigue involving old enemies, new threats, and personal demons, challenging him to redefine himself both as a hero and as a man.