After his girlfriend mysteriously disappears from a cruise, Sean Walker discovers a conspiracy of global proportions.

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.

The administration unveils a tough new strategy to force Sophia to reveal the detainees' plan; Vicky and Carter possess a crucial hostage.

The White House grapples with a mysterious biological threat. Their only hope is to crack Sophia during interrogation. Meanwhile, Vicky and Carter keep their hostage captive while they await further instructions. FBI Agent Collier, on her search for Leila, stumbles upon Vicky's secret life. Elsewhere, a powerful businessman, Dempsey with classified intelligence and ties to the White House, emerges from the shadows.

The CDC tries to identify the contagion and treat those infected as the biological threat intensifies; Simon asks Sophia to betray Thomas.