In the wake of an alien occupation that decimated the majority of the human population, Tom Mason is named second-in-command of the 2nd Mass (Massachusetts). When on a supply run, his son Hal sees his brother Ben who was enslaved by the aliens.
A scouting mission is derailed when a band of outlaws captures Tom and his squad and tries to leverage them to get hold of the 2nd Mass' weapons.
Dr. Michael Harris comes up with a way to save the enslaved children. Tom discovers that saving his son could mean death for the other captive children.
As Tom and his squad search for any salvageable vehicles, Rick tries to help the aliens. Anne and Harris clash over their different plans for a captured alien.
Hal comes up with a risky plan to rescue his brother. Anne discovers a way to kill the aliens.
The leader of the 7th Mass alerts the 2nd Mass of an impending attack. Hal takes notice of the changes in his brother.
As Terry's nefarious plans come to light, Tom attempts to strike a compromise to get the children back.
As the 2nd Mass plans to take the fight to the aliens, a scouting mission uncovers Weaver's traumatic past and reveals a third humanoid alien species.
With no word from several Mass units, Tom and Weaver clash over the 2nd Mass' plans for the upcoming attack. Tom struggles to process Anne's latest discovery.
With their odds being so low with the destruction of the other Mass units, Tom oversees the evacuation of civilians as Weaver sets up for a major fight. Tom has to make a difficult decision in order to save his son.