Chandler and his fractured team join forces with an underground resistance in an attempt to defeat Amy Granderson; Rachael tries to help the sick while remaining a prisoner; Sidney and the crew try to regain control of their ship.

Slattery and the crew of Nathan James are in a race against time to save an injured Dr. Tophet and regain control of their ship.

The ship goes to Norfolk so that the crew can check on their families. And Chandler gives them the opportunity to decide if they want to continue or remain. Something even he is considering.

The crew makes a discovery; Chandler sees an opportunity to add another ship to the fleet.

Chandler and his crew face off against a nuclear-powered submarine led by British naval officers.

Chandler tracks the immunes to Northern Florida; Rachel comes across a secret formula.

Slattery struggles to evade the sub; Chandler and the land team infiltrate the immune compound.

Chandler and his team set out to find supplies and materials for Dr. Scott's lab, only to tangle with bounty hunters and the Immunes. Meanwhile, Rachel's effort to find a spreadable cure depends on the scientist who nearly erased mankind.

Rachel is hard at work on a new, more efficient version of the cure while Alisha decodes a message found on a cell phone recovered from the Immunes on land.

Sean Ramsey broadcasts a message implicating the Navy in a devastating disaster.

The Nathan James is trapped between the sub and the civilian blockades set up by the immune. Chandler sends Dr. Scott off the ship under Slattery's protection.

As small Immune factions continue to fight the cure, CDR Chandler, and his team, put a call out to civilians to meet them at ports all over the United States to receive the cure.