Set on a future Earth, Defiance introduces players and viewers to a world where humans and aliens live together on a planet ravaged by decades of war and transformed by alien terra-forming machines. It centers on Jeb Nolan, the law-keeper in a bustling frontier boomtown that is one of the new world’s few oasis of civility and inclusion. Nolan is a former Marine who fought in the alien conflict and suffered the loss of his wife and child in the war. The trauma transformed him into a lone wanderer in the wilds of this new and dangerous world.
As the story of Defiance resumes, the lives of the townspeople are in drastic turmoil. The Earth Republic has assumed control of the town, with far-reaching consequences including a new mayor. Nolan traverses the badlands to find a lost Irisa, Amanda has an unexpected new role in the town as she searches for Kenya and the Tarr family desperately tries to keep control of their criminal empire in the midst of dramatic changes.
In the year 2046, it's a new Earth - with new rules. Over thirty years after various alien races arrived on Earth, the landscape is completely altered, terraformed nearly beyond recognition. To the town of Defiance, on what used to be St. Louis, comes the mysterious Nolan and his charge, Irisa.
Following the events of the season two cliffhanger finale, season three of Defiance opens on the eve of an impending military siege upon the town, which has fallen on hard times following the collapse of its lucrative mines.