- This section uses info from Wikipedia
A mother and father, with the infant Nux, travel to the Citadel where they live on the ground in poor conditions, without adequate supply of food and water. To support his family, Nux's father takes up a job at the top of the Citadel; however, unbeknownst to him, the job is very hazardous and he eventually dies due to the conditions. Nux never finds out what happened to his father, and his sick mother dies later. Believing his father is still alive, he tries to reach the top of the Citadel by grabbing onto the elevator used by the guards to transport to the top. One of the guard is about to push him off, but he is stopped by another guard who wants to see how long Nux can hold on. Nux desperately tries to hold onto the edge of the elevator, even as he starts to slip. The War Boys watching him start laughing, to which he laughs back in a mocking response and refuses to let go. Upon seeing this, the War Boys and guards are stunned by his grit. A guard who is impressed by his determination saves him from slipping and pulls him up to the platform. Impressed by his grit, the War Boys call him "a hard nut to crack", which leads to him being named "Nux". He eventually joins the War Boys when he grows up and Immortan Joe becomes like a father figure to him.
The second part focuses on the origins of Immortan Joe and how he acquired his godlike status. After the society started collapsing, war veteran Colonel Joe Moore formed a raider gang, along with other soldiers who served under his command such as Major Kalashnikov, and started raiding the communities in the wasteland. During one of his raids, a captured fat man who is about to be executed reveals the location of a fortress with huge natural stone pillars sitting atop a massive aquifer, in exchange for a deal for sparing his life. However, he warns that it is heavily defended and nearly impossible to enter without being granted access by those inside.
Joe first tries to convince the defenders of the aquifer to allow him to access the fortress, by offering them several women as sex slaves. However, when they refuse, he launches an all-out assault on the fortress, but the siege lasts for many days, killing many of his followers and rapidly depleting their supplies of food and water. He sends his scouts to search for more supplies, but they fail to find any; however, they report the discoveries of an abandoned oil refinery to the north, and a lead mine to the west of the fortress.
He then draws up a plan to climb to the top of the fortress by sending up a monitor lizard to the fortress with his men tied by the rope to the lizard which will allow them to scale the walls. The lizard at first keeps coming back down every time until one of Joe's henchmen cuts off his own finger and attaches it to a rope, using it as a treat to motivate the lizard to scale all the way to the top of fortress, thus allowing Joe and his henchmen to climb it. The plan initially backfires, as most of Joe's followers are killed, and one-by-one, the inhabitants of the fortress begin executing his surviving men and hanging the corpses of his dead followers from the cliff walls. Many of Joe's followers on the ground, believing Joe to be dead, accept defeat and prepare to leave by the dawn of the third day.
However, Joe reemerges with his few remaining followers, having killed all of the defenders. His followers are stunned by this nearly impossible victory and call him "Immortal". This eventually leads him to acquiring the name of "Immortan Joe". The fortress comes to be known as Citadel and becomes the base for Joe and his army. His men eventually start operating the previously-discovered oil refinery and lead mine to generate oil and bullets. The oil refinery is later named "Gas Town" and the fat man who told Joe about the fortress, who later comes to be known as "The People Eater", is made its leader. The lead mine is named "The Bullet Farm," and Joe's second-in-command Kalashnikov, who later comes to be known as "The Bullet Farmer", is made its leader. The story also explains how Joe had three sons; Scrotus, Rictus Erectus and Corpus Callosum, all of whom were either deranged, mentally challenged or deformed, paving the way for Joe's plan to father healthy sons who could carry on his legacy by using various women as his wives who would be isolated from the harsh elements of the wasteland, thus increasing the chances of his sons being born healthy.