Two centuries after a disaster reshaped the surface world, an attack on the underground community of Vault 33 prompts young Lucy MacLean to venture into a dangerous world. Meanwhile a man named Maximus aspires to join the Brotherhood of Steel, and a group of bounty hunters resurrects a mutant from the old wold.
Lucy explores the remnants of the surface world and finds a survivor with an unsettling warning, and a survival mission of his own. As squire to a fully armored Titus, Maximus finds himself on a retrieval mission that goes wrong.
With the Ghoul hot on her trail Lucy attempts to find Moldaver, only to lose the one thing she needs to bargain for her father. Maximus' attempt to repair his armor leads him to even worse trouble with the locals, and back in Vault 33 Norm gets a new duty assignment.
Lucy's unsuccessful efforts to escape the Ghoul bring her to a place where she must adapt to the ways of the Wasteland if she is going to survive. Meanwhile, Norm grows suspicious that they don't know the full truth of what happened inside Vault 32.
Maximus' decision to trust his new squire has disastrous consequences. But after Lucy finds him, the two set out together in search of the head. As Vault 33 elects a new overseer, Norm grows suspicious of their leaders.
The Ghoul recalls his past as Cooper Howard, whose happy family life and thriving ad career are threatened by hard truths about his new employer. Lucy and Maximus wake up inside Vault 4, which Lucy is surprised to find populated by people mutated by surface radiation.
In search of a mark, the Ghoul pays a visit to a homesteading family – while in the past Cooper Howard is approached to spy on his new employers. Lucy finds herself at the mercy of Vault 4's justice system, and Norm reaches out to his neighbors.
Maximus is forced to come clean before the Brotherhood, who are looking to forge a new power base in the wasteland. Meanwhile Lucy arrives at Moldaver's compound, where she is forced to confront the truth about her father. Norm enters Vault 31.
