Recap of Iron Man 3.
Ever since the Battle of Manhattan seven months ago, Tony Stark, the Iron Man, is a changed man. Having confronted threats from beyond his homeworld and nearly died saving New York from destruction, he has become shell-shocked, spending several restless nights building new Iron Man suits, causing friction with his girlfriend Pepper Potts, while doing the best he can to hold himself together...
One day, however, a new terrorist known as the Mandarin makes himself known to the world, taking responsibility for a series of bombings on US army bases, as well as on American soil. In one bombing at the TCL Chinese Theater, Tony's best friend and SHIELD agent Happy Hogan is seriously injured and rendered comatose. Enraged, Tony publicly challenges the Mandarin, disseminating his home address in Malibu.
After returning home, Tony is approached by a figure from his past: Maya Hansen, a biologist whom he met and seduced in 1999. Hansen now worked for Advanced Idea Mechanics — "AIM" — a think tank that had given her the resources needed to work on her personal project: "Extremis", a revolutionary medical treatment. Hansen has concerns with how her project is being used, but before she could entreat Tony's help, gunships converge on his home, laying siege with a barrage of missiles. Tony manages to save Hansen and Pepper, before barely escaping with his life in a prototype Iron Man suit.
As the world believes him to have died in an attack from the Mandarin, Tony crash-lands in rural Tennessee, near a town he was looking into while investigating the Mandarin. With his suit damaged and out of power, Tony enlists the aid of a young boy to help him with some repairs while he looked into a bombing that took place in the town, which had been carried out by a soldier who, allegedly, went insane and killed himself and five others in a suicide bombing. Tony's investigation into the bombing revealed heat signatures that matched the bombing at the TCL Chinese Theater, which eventually leads to the discovery that the "bombings" were actually caused by Extremis: when a patient's body rejects the Extremis treatment, it causes a violent and deadly explosion. AIM had been manipulating public perception by pinning the Extremis explosions on the Mandarin. In the course of his investigation, Tony is also confronted by AIM assassins who were also Extremis patients, their bodies capable of generating enough heat to melt steel. Tony manages to fend them off, and manages to track the Mandarin's location to Miami.
Tony makes his way to Miami and comes face-to-face with the Mandarin, only to find that he is not a terrorist mastermind. In reality, the "Mandarin" is Trevor Slattery, a disgraced British actor with a sordid history of drugs and controversy whom AIM hired to act as the Mandarin, all the while keeping Slattery ignorant to the fact that he was being used as the public face of a terrorist campaign. Tony is then confronted by AIM's leader — Aldritch Killian, a scientist whom Tony briefly met in 1999. At the time suffering from severe physical disability, Killian wanted Tony's help in AIM, only for Tony to snub him. Enraged, he would later hire Hansen, co-opt her Extremis research to cure his disability, then expand the research to experiment on injured war veterans, some of whom now worked as Killian's enforcers, and others of whom died due to Extremis causing their bodies to explode. After killing Hansen once her usefulness had ended, Killian reveals he had captured Pepper and subjected her to Extremis, hoping to keep her as a trophy while taking over the United States by hijacking the "Iron Patriot" armor used by Tony's friend, James "Rhodey" Rhodes, and using it to kidnap the President while setting up a puppet leader.
Tony fights free from captivity and, as Air Force One is attacked and President Ellis is kidnapped, saves those who had fallen out of the plane before making his way to an impounded oil rig, where Killian intends to have President Ellis killed on live TV. As Rhodes rescues President Ellis, Tony summons his entire collection of Iron Man suits, controlled by his personal AI "JARVIS", to attack Killian's goons while Tony confronts Killian. In the ensuing fight, the Extremis-empowered Pepper saves Tony and slays Killian for good and all.
As a sign of his devotion to Pepper, Tony instructs JARVIS to self-destruct all of his Iron Man suits. As Pepper undergoes treatment to have Extremis removed from her body, Tony also undergoes surgery to have the shrapnel that had been embedded in his heart years ago removed, allowing him to live without having to rely on his arc reactor. His past demons finally laid to rest, Tony returns to the ruins of his Malibu home and tosses his now-obsolete arc reactor into the ocean.