Lt. Abbie Mills and Ichabod Crane search for Abbie's estranged sister, Jenny, 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.

When Ichabod Crane goes missing, his wife, Katrina, appears to Lt. Abbie Mills in a vision warning her that the Headless Horseman will return to Sleepy Hollow by nightfall. A frantic Abbie seeks help from the mysterious Henry Parrish, who holds vital clues about how Crane can vanquish his dangerous blood tie to the Horseman. Meanwhile, an encounter from Crane's past weighs heavily on him, and details about his first encounter with Katrina are revealed.