Still adjusting to his 21st century reality, Ichabod Crane and Det. Abbie Mills move forward in their mission to unravel the mysteries lurking in Sleepy Hollow. A frightful vision from Ichabod's former wife Katrina, sends the unlikely duo on the hunt for a vengeful witch from the 1700s who has been awoken by unknown evils and is on a path of destruction in the quaint town. Meanwhile, despite all odds, Officer Andy Brooks is back and on a questionable mission of his own.

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.

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

Henry sets out to find the Gehenna Key, which will allow his master Moloch to escape from Purgatory with an army of the damned. Meanwhile, Ichabod tries to free himself from his buried tomb, and Jenny must escape the Hessians holding her on Henry's behalf.