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.

Ichabod, Abbie, Capt. Irving and Jenny Mills unite against the Headless Horseman; information about the Horseman's motive shocks Ichabod.

Ichabod and Abbie concoct a daring plan to try to rescue Ichabod's wife from the Headless Horseman by resurrecting a Frankenstein-like monster created by Benjamin Franklin. Frank faces new trouble after revealing the true details of his encounter with a demon. Jenny finds herself at odds with the new sheriff in town.

After escaping Purgatory, a warlock who triggered the Salem witch trials returns to find a dangerous book of spells. Meanwhile, Abbie attempts to trust Frank Irving again, while Henry struggles to find his identity.

The town of Sleepy Hollow and its inhabitants are permanently changed; a relationship is destroyed beyond repair.

On an FBI team-building day, Abbie and Sophie come face to face with a monster that may finally blow their cover with Reynolds. Meanwhile, Jenny and Joe find themselves in possession of something precious and Crane discovers that the symbol from the Catacombs may be more important than he realized.

As The Hidden One grows stronger, Crane must examine his past with Betsy Ross to find the key to stopping him. Meanwhile, Jenny wonders if she can ever have a relationship with her father, and Abbie faces a hard decision as things with Reynolds become more strained.