The four survivors begin manifesting strange symptoms, but Eph and Nora's attempt to quarantine them is thwarted as the disinformation campaign begins. Meanwhile, in jail, Setrakian receives a surprise visit from an old - a very old - acquaintance.

Eph and Nora fight to save Captain Redfern's life before coming face-to-face with the horrifying effects of the virus. A spike in rat attacks signals Fet that something inexplicable is happening deep below the city. Released from jail, Setrakian begins his own merciless plan to stop the spread of the disease.

With Nora gone, Eph reluctantly joins Setrakian's quest in hopes of gathering enough evidence to warrant a citywide quarantine. Fet encounters the unexpected inside the subway tunnels, and a medical emergency threatens Palmer's master plan.

After warning Kelly to leave the city with Zack ahead of the spreading plague, Eph is arrested by the FBI. Eichhorst has one final job for Gus, while Setrakian realizes that the coming eclipse is the tipping point for virus infection and the beginning of the end.