In the final season, Jason Hayes struggles to balance his warrior’s existence with the responsibilities of single fatherhood. Ray Perry, his trusted second in command, questions whether he will be able to leave the battlefield behind as his retirement nears. Dedicated door-kicker Sonny Quinn battles against changing tides as Jason and Ray’s shifting focus means that other teammates must shoulder more responsibility. Both Omar Hamza and Drew Franklin find diving into work an effective way to distance themselves from their past traumas. Vital to mission success is Lieutenant Lisa Davis, a no-nonsense officer who ushers the team into a new era of warfare against powerful rivals for supremacy on the world stage. Ripped away from their loved ones at a moment’s notice to be deployed across the globe, Bravo team remains dedicated to their duties. Even in the face of overwhelming odds, they know this is the price to keep the families they left behind safe.

　　近未来某一年，地球爆发毁灭性极大的致命病毒，从而导致全球超过半数的人口死亡。一望无际的茫茫大海，似乎成为病毒无法涉足的神域，而汤姆·坎德勒船长（埃里克·迪恩 Eric Dane 饰）所统领的阿利·伯克级驱逐舰导弹驱逐舰“内森-詹姆斯”号，则成为天罚过后漫无目的漂流并等待 赦免的诺亚方舟。为了保存有生力量，同时确保船上的两名滤过性病原体学者研制出抗毒解药，坎德勒船长违抗了美国临时政府的召唤，带着船员踏上漫漫征途。然而一路上凶险倍至，为了补给和疫苗，他们不得不停靠港口和陆地，除此之外更有他国的船舰试图抢夺解药。更可怕的是，绝望和恐慌也在船员间蔓延。看不到未来的旅程，何日才是尽头……
　　本片根据同名小说改编。

　　历史频道宣布续订《骑士陨落》第二季。