Lt. Abbie Mills and Ichabod Crane search for Abbie's estranged sister, Jenny Tag Team, who has escaped from a Sleepy Hollow psychiatric hospital. In a game-changing episode, which includes flashbacks to the real Boston Tea Party, Abbie and Ichabod discover more about the evil they are facing... and finally learn its name in the haunting.

When an unidentified boy is discovered in Sleepy Hollow, Ichabod Crane and Lt. Abbie Mills are called to the scene. After speaking with the child, they immediately realize that something sinister and sickly is afoot and the duo go on a hunt to discover his home and origins - and are shocked by what they find.

When Capt. Iriving's daughter, Macy, becomes the target of evil forces, he makes a desperate plea to Crane and Mills for help, and seeks answers that lie within Washington's Bible. Meanwhile, a frightening chapter of Jenny's past is revealed.