The arrival of an odd young boy (Matthew Lintz) with unusual symptoms (including an unknown illness and the ability to only speak Middle English) brings the CDC to Sleepy Hollow to stop the spread of any possible infection. After speaking briefly to young Thomas, Ichabod Crane (Tom Mison) believes he may have lived in the lost colony of Roanoke. Taking Abbie (Nicole Beharie) into the woods in search of the boy’s origins where they find an entire colony of Middle English folk all infected with the same disease which is already spreading through Sleepy Hollow.
The only way to save both the boy, and those in Sleepy Hollow, from the curse of Pestilence spreading far and wide enough to allow the Horseman to ride openly, is to return Thomas to to the isolated descendants of Roanoke. However, this becomes harder to achieve once Ichabod is infected with the plague and quarantined by the CDC. While unconscious with the disease Ichabod encounters Katrina (Katia Winter) in the limbo between life and death where she is kept as a prisoner of Moloch.
In the episode’s B-story, a jealous and nosy Morales (Nicholas Gonzalez) begins poking into the cover story of Ichabod as a visiting professor from Oxford despite Captain Irving‘s (Orlando Jones) express orders to drop the matter. Believing the only way to cure Ichabod and Thomas is to return them to the spring of Roanoke, Abbie enlists the help of Irving to steal the two patients away in hopes of a miracle.