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.

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

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

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

With nations being rapidly occupied, Chandler tries his hand at diplomacy to unite two hostile countries so they can fight a common enemy.

The crew of Nathan James begin preparations for what may be their most ambitious mission to date.