Duke Nukem, a civilian living a normal life of luxury as a Hollywood celebrity. Being a womanizer, Duke lived in the fast lane; he was considered a role model and hero. While going on a TV show to comment on his new published book: Why Am I So Great. He became a popular man because of this book, however a man named Dr. Proton sought to kill Duke, and captured him. Putting him in a galactic prison, Duke Nukem escaped, and then sought out to seek revenge on Proton.
Going through many battles and death courses, Duke Finally caught up to Dr. Proton. An epic fight ensued and killed Proton. Dying, Dr. Proton mentioned that he was merely a pond in a bigger scheme, saying that he took Duke away from earth to make way for his emperor. Originally he was supposed to kill duke, while his Emperor invaded earth, with duke out of the equation. Duke shocked by this, he slowly strapped Proton on his throne in the cockpit of his ship.
 Duke Nukem went to the ships control console and set a course for the sun. Duke then escaped, by an alien ship in the docking bay. Going back to earth, Duke was thought to be dead. The Cycloid Emperor and his Queen took over earth, assuming that Proton did his job in killing Duke. Duke returning to earth, crash-landed in Los Angeles, one of four that were ground zero of the invasion, seeing that the world he once knew was now a barren wasteland. Duke Nukem took shelter on a rooftop of an abandon building nearby; there he contemplated a plan to save humankind. One day a young woman, wounded walked in the abandon building Duke was hiding in. Duke found her and aided her back to heath. She told duke that her name Angelina. She was a refugee from a death camp, once a military sergeant for the EDF (Earth Defense Force), she mentions that she escaped. Saying to duke, that in his absence, the aliens took over, with no one to stop them Earth was open for an attack.
Dying in Dukes arms, she gives him a keycard to an underground facility that would help him with his vendetta.   
Duke Nukem took all the weapons he could find in the underground facility and with a vendetta, he started using guerrilla tactics on the aliens and started a rebellion. One after another, destroying key bases crucial to the Cycloid Emperor’s plan, Duke was slowly but surely slowing down the Emperor’s vision.  People heard of a man that rebelled against the aliens. The Emperor assured the humans that were in the death camps at the time, which this terrorist will be apprehended. Duke began killing off key generals responsible for earth’s takeover: the Battlelord, the Overlord, and finally killing the Emperor himself.