MODOK makes a robot and Cap has to fight it, a tale called: Mission: Stop the Cyborg!
But before that, Captain America has another fight with Sharon and decides he doesn’t want to have to worry about her safety any more, so he tries to force Nick Fury to give her a desk job.
During the conflict with MODOK, Cap mistakenly believes that Sharon Carter betrayed him. This makes him want to stop living.
Rather than talk it out, they break up. In his sadness, Cap goes to Vietnam to help out a doctor who is treating people injured on both sides of the war. Because it’s in an Asian territory, Mandarin shows up.
