The crew of a lone naval ship try to save humanity when they discover a deadly virus has wiped out most of the population in the series premiere of this drama.

The crew members arrive at the Guantanamo Bay military base to collect food, fuel and medical supplies. When they come under attack by escaped Gitmo prisoners, they team up with a gruff private contractor to push back against the offensive.

The crew faces a new foe targeting Rachel and her research, leading Chandler to engage in a series of dangerous strategic maneuvers.

Chandler's leadership is put to the test when the ship's propulsion system is in danger of breaking down, the crew becomes overworked and exhausted, and Dr. Scott could potentially lose all of her research on the virus.

With Rachel close to a breakthrough on her vaccine, she, Chandler and XO Slattery lead a small team into the jungles of Nicaragua on a mission to find monkeys for her vaccine trials. While there, they find much more than they bargained for when they run across a former drug kingpin who will stop at nothing to maintain his stranglehold on his oppressed society. Chandler and his men find themselves in a huge moral dilemma over whether to eliminate this menace or take what they need and continue on with their mission.

After returning from the horrors of Nicaragua, panic begins to spread throughout the ship when Lt. Danny Green comes down with a mysterious illness that could be the virus. Losing faith in Rachel and her failing vaccine trials, Chandler now has to deal with a restive crew. If he fails to keep the crew together, the whole mission is in jeopardy.

After picking up a distress call near Jamaica, Chandler and a small team stage a rescue attempt. But a surprise attack leave Chandler and Tex stranded at sea. Slattery and the crew search desperately to find their lost at sea Captain and his comrade, hoping to do so before their enemies beat them to it.

With Chandler and Tex caught in a dangerous situation, Slattery has to step into the role as commanding officer. Torn between a mission with the fate of the world at stake and a Captain (and friend) in danger, Slattery has to find a way to get his people back without losing the most important asset: the vaccine prototype.

Rachel and Chandler ask for six volunteers to participate in human trials of her vaccine, but the tests could be a living hell as the virus and the vaccine do battle inside their bodies. Meanwhile back in the States, Chandler’s wife and father are doing everything they can to keep their family alive.