With doubt still surrounding the tragedy at the White House, Sterling encounters an unlikely ally in Simon, who risks his life to return with a possible antidote. Against the wishes of Chief of Staff Richard Peel, Jarvis authorizes an air strike to neutralize them. Meanwhile, Sophia continues on her diabolical plan to exterminate the human race, now with the help of an unwitting accomplice -- Leila
The Sleepers mourn their losses after negotiations are derailed; Sterling tries to test Simon's loyalties; President Martinez asks Sen. Lewis to find any remaining moles in the White House.
Negotiations for the release of the Sleepers begin after Sophia triggers a national disaster; Sean and Vicky continue their mission.
Martinez and his Chief of Staff order their intelligence departments to determine the nature of Thomas' message and who it was sent to. Meanwhile, Thomas launches a surprise attack, Alaskan Senator Catherine Lewis threatens to go on national television to alert the public to the enemy among them, and Sean and Leila get a fresh lead on Samantha's location.
Sophia's suspicions are confirmed when Thomas reveals a shocking new plan. Leila and Sean battle mercenaries while searching for Samantha.
Sean encounters a mysterious conspiracy theorist while looking for answers in Leila's home; Simon's allegiances are tested.
The CDC tries to identify the contagion and treat those infected as the biological threat intensifies; Simon asks Sophia to betray Thomas.
The administration unveils a tough new strategy to force Sophia to reveal the detainees' plan; Vicky and Carter possess a crucial hostage.
The president's staff grapples with a new reality; the conspiracy engulfs an FBI agent and a mercenary with questionable ties; a shadowy figure emerges with knowledge of the detainees.
After his girlfriend mysteriously disappears from a cruise, Sean Walker discovers a conspiracy of global proportions.