We start with Tony learning from Jocasta that he doesn’t have heart problems anymore because his sentient armor replaced his biological heart with a special artificial one. If it were me and my armor recently came alive and tried to kill me, I’d be suspicious. But he’s not.
I don’t know why we even bother with the heart stuff anymore. It seems to flip back and forth without any real reasons.
Anyhow, a dude named Sun Tao is part of a cult called the Sons of Yinsen. Their leader, Professor Yinsen, was the guy who was with Tony Stark when he was captured by Wong Chu. It also turns out that Wong Chu–the dude who captured Tony Stark and first inspired him to become Iron Man–is still alive and is a drug lord.
He’s also fat and hideous.
The Sons want to capture him and stop his evil drug trade–and also Wong Chu has Professor Yinsen captive.
Iron Man helps take down Wong Chu, who is killed in the conflict. Professor Yinsen is also killed, but the Sons save his brain and also manage to find out where the destroyed sentient armor is located so…Yeah, he’ll be back.