A dysfunctional blended family is forced together when son Nick is hospitalized after an accident outside a drug den -- where he believes he has witnessed his friend turned into a flesh-eating killer. After Nick disappears, his mother Madison slowly realizes that a reported virus may actually be the beginning of something much, much worse.

Madison returns to the high school in an attempt to help her son, forcing Alicia to keep vigil over Nick during his drug withdrawal. Meanwhile Travis goes in search of his son Chris, who has stepped into the middle of a riot breaking out in the middle of Los Angeles.

Madison and her kids deal with the threat of a home invasion while awaiting Travis's return. Meanwhile, Travis and his family are forced to flee their safe haven with the Salazar family, only to have one of their group suffer an injury.

The family tries to adapt after the National Guard roll into town and fortify their neighborhood with a border fence. While Travis is called upon to intervene with a distraught neighbor, Chris convinces Madison that someone is alive and in need of help in a house visible several miles away. Meanwhile, Liza shows a government doctor around the town.

Travis asks to visit to the triage facility where the group's loved-ones have been taken. Meanwhile Daniel holds a soldier captive in the hopes of learning the truth about his wife, leading to a revelation about the National Guard's plans.

Travis and Maddie prepare to flee Los Angeles with their families, but find it difficult to rescue Nick and Liza after the military compound is overrun by an army of the dead.