After the horrifying revelations and reversals of fortune in Baltimore, Chandler and his fractured team join forces with an underground resistance in an attempt to defeat Amy Granderson. With doses of the cure running low, Rachel tries to do some good for the sick while remaining a prisoner at Avocet. Meanwhile, 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.

After the horrifying revelations and reversals of fortune in Baltimore, Chandler and his fractured team join forces with an underground resistance in an attempt to defeat Amy Granderson. With doses of the cure running low, Rachel tries to do some good for the sick while remaining a prisoner at Avocet. Meanwhile, 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.

Nathan James returns home to Norfolk on a mission. With his family now safely aboard the James, Chandler sends his crew in search of their friends and loved ones.

The crew of Nathan James discovers that hospital ship USNS Solace was sent to sea to wait for Dr. Scott's cure. Captain Chandler sees an opportunity to add another ship to their fleet while Rachel is eager to find a lab better equipped to replicate the vaccine. When Solace fails to respond to radio communications, Chandler and his team board the ship...and come face-to-face with an unexpected enemy.

With a small group of survivors from Solace in tow, Chandler and his crew square off against an enemy of the most dangerous kind - a nuclear-powered submarine led by rogue British naval officers, Sean and Ned Ramsey. XO Slattery interrogates a captured mercenary from the hospital ship in an effort to extract information on the sub and its mission. As Nathan James engages in a perilous game of cat-and- mouse, the truth about the mercenary sub unfolds.

Chandler tracks a new threat to Northern Florida. Meanwhile, Rachel comes across a secret formula that her mentor, Dr. Hunter, had been perfecting.

While XO Slattery struggles to evade a submarine, Chandler and his team infiltrate a compound on land.

Still trying to piece together Dr. Hunter's lost formula, Rachel grapples with her sworn enemy's presence on board the Nathan James.

With Dr. Scott on the verge of a breakthrough, Chandler and his team set out to land in search of much needed supplies and materials for her lab.

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

After a message is broadcast implicating the Navy in a devastating disaster, Chandler looks to infiltrate the network and regain the trust of the American people.

Nathan James finds itself trapped between the submarine and civilian blockades.

With their mission now fully dedicated to spreading the cure, Nathan James puts a call out to civilians to meet at pre-selected ports across the country.

CNO Tom Chandler is sent to Asia to investigate a possible mutation of the Red Flu. Captain Slattery and his crew deliver cure to Southeast Asia but there may be an unexpected threat in the region.

Chandler must find a way to return to his old crew and investigate a dangerous new foe.

Chandler and crew race to find answers in an Asian Dodge City. Slattery begins to unravel the truth about his troubling predicament.

Chandler must confront his suspected new foe. Slattery learns more about the supposed virus mutation. Pressure mounts on President Michener as the situation worsens.

Chandler's mission becomes complicated as his position is worsened. President Michener faces pressure from the regional leaders.

Chandler's mission comes to a head as he prepares the final part of his plan. President Michener ponders the fate of his presidency.

The Nathan James must evade an overwhelming threat. A revelation in St. Louis puts President Michener in a terrible position.

America copes with tragedy while Chandler further investigates the possible virus mutation.

Chandler gets a lead that could help answer threatening questions. Kara does some digging in the White House.

Chandler finds himself making a difficult decision when an order comes in from the White House.

Chandler faces his powerful enemy in a final showdown. Kara joins someone that can help with her mission.

Chandler returns to America to find out what has really been happening.

The fight for America comes to an end; Chandler faces a challenge that could change his life forever.