Abbie Mills receives a message from Ichabod Crane after not hearing from him for several months. They now become aware of a new evil that must be addressed, and join forces with old friends to face this new threat to Sleepy Hollow.
Pandora unleashes a monster that haunts Sleepy Hollow residents at night, which tempts Abbie and Jenny to face a painful chapter of their lives. Meanwhile, Ichabod draws on his own experiences to offer Abbie advice when she must make an important decision about her career.
When Reynolds heads to D.C. to discuss developments in the Nevins case, Abbie is left in command. Jenny and Joe deal with unexpected consequences as a result of stealing the shard, which leaves both the lives of the heroes and Abbie's career in great peril. Meanwhile, a new, more dangerous evil force is revealed.
In the aftermath of Jenny and Joe's run-in with Sophie, Abbie is in deep water with Reynolds. Meanwhile, the Witnesses deal with lasting implications of the shard and find themselves in grave danger as they come face-to-face with a greater evil than they could have imagined.
In the quest to save Abbie, Crane and Sophie are forced to battle a supernatural force targeting the citizens of Sleepy Hollow, while Pandora and The Hidden One only grow stronger. Meanwhile, in an effort to find out what truly happened to her sister, Jenny faces an old foe: her father. Can our heroes solve their most personal case yet?
When Jenny makes the decision to confront her father, family turmoil from the past rises to the surface. Meanwhile, Atticus Nevins returns to town, bringing more danger than the FBI could have imagined.
As a monster resembling the New Jersey Devil ravages Sleepy Hollow, Crane must draw on his past to find the connection. Meanwhile, Jenny and Joe stumble as they navigate their new relationship and Abbie continues to struggle with the aftermath of her trauma.
Abby and Agent Foster go on a two day FBI survival training course and encounter one of the creatures summoned by The Hidden One. Crane attempts to find out more about the symbol from the world Abby was trapped in.
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.
After a startling discovery, Abbie and Crane realize what they must do in order to make Pandora's box complete again. Meanwhile, the team works tirelessly to stop The Hidden One, before he destroys all of humanity.