When a scavenger and his daughter arrive in the alien-populated, frontier town of Defiance, they find themselves caught up in an inter-species blood feud and an impending invasion by a powerful alien army.

Nolan and Rafe go into the underground mines and the buried city of Old St. Louis in search of a runaway Votan criminal. Meanwhile, Irisa interferes with a ritual she finds morally abhorrent, drawing the ire of Datak.

Nolan and Irisa investigate "Hellbugs" that rip apart their victims from the inside-out, and learn that someone is using them as a weapon. Meanwhile, Irisa suffers from disturbing visions.

Kenya and one of her girls are kidnapped and forced to run for their lives from a Volge warrior, while Amanda and Nolan turn to Datak for help finding the two women.

When a transport vehicle stops in Defiance, Nolan takes the opportunity to escorts a prisoner out of town. Irisa takes extreme action when she recognizes a man she believes tortured her as a child.

Nolan is reunited with an old war buddy who is tracking a Castithan war criminal, who manages to escape custody. Meanwhile, Quentin McCawley must decide whether to destroy the alien artifact sought by the duplicitous former mayor.

The town braces for an approaching storm of debris falling from space, pushing the McCawleys into a confrontation with Nicky. Irisa and Nolan journey into the Badlands to find the Spirit Riders after she has a disturbing vision of their leader, Sukar.

Nolan and Tommy discover a famous astronaut from old Earth who has been in suspended animation for decades, and who comes to believe he was experimented upon by Votans.

The outbreak of a plague in Defiance leads the town council to quarantine the Irathients in the mines, turning Irisa against Rafe's men. Meanwhile, Quentin is given startling news about his mother.

The remains of the previous owner of the NeedWant are found inside a wall, pointing to a long list of suspects. Meanwhile, Datak makes a decision on the eve of his son's wedding.

On the eve of the mayoral election Nolan receives a warning about a potential threat to Amanda Rosewater's life. But when he acts to prevent it, the lawkeeper himself is thrust into the middle of a plot to undermine Amanda's credibility. Meanwhile, Irisa falls victim to a mysterious ailment connected with Doc Yewll's secret project.

While the town citizens cast their votes for the next mayor, Earth Republic mercenaries search for Irisa and the Votan tech hidden inside her. Stahma fears for her life after Datak learns a secret.