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.

Abbie and Ichabod look for clues to stop the evil in town; Abbie receives an unexpected visit from Andy Brooks.

Ichabod enlists Henry Parrish to help him communicate with Katrina, but in the process, a menacing danger is unleashed from purgatory.

The battle between good and evil comes to an explosive head – sacrifices must be made, worlds collide, loyalties are tested and the town of Sleepy Hollow will never be the same