Abbie takes Ichabod to a Little League baseball game and explains that she likes baseball because it has tradition, teamwork, and a lack of discrimination. She points out that Ichabod and founding fathers fought for those very things, and he joins in, heckling the umpire. After the game is over, Ichabod admits that he felt that he was home for one moment, and Abbie assures him that he is. As they go to Abbie's car, Ichabod says that he knows enough about the town to find his way around and wants to take a walk on his own. Once Abbie leaves, Ichabod walks to the cemetery and visits Katrina's grave. Someone shoots him with a tranquilizer dart and he collapses.
As Abbie drives home that night, she starts to doze off. She suddenly finds herself in an old-fashioned home with a baby crying in the next room. When Abbie goes to investigate, she finds a sinister-looking doll in the crib. The Horseman comes stomping into the room and Abbie flees before him, taking refuge in a downstairs rooms. As she locks the door, Abbie discovers a group of robed witches chanting in Latin. Katrina appears and introduces herself, and explains that the house is an echo of the house where she and Ichabod resided when they were married. Katrina is able to reach those who bear witness through their dreams, and has contacted Abbie to warn her that the Horseman will return with nightfall. He can only be stopped by the two Witnesses, but Katrina warns that Ichabod has been abducted and warded against her abilities. The imprisoned witch believes that her husband's abductors plan to use his blood tie to the Horseman, and tells Abbie that she must find a Sin eater who can sanctify Ichabod and break the blood tie to the Horseman.
Before Katrina can say anything else, Abbie jerks awake as a truck approaches her car. She swerves off the road just in time to avoid a collision.
The next day, Abbie tells Irving what happened. He's skeptical about the story but Abbie warns that they can't harm the Horseman without hurting Ichabod. She refuses to abandon her friend and Irving asks what she needs. In reply, Abbie says that she needs to meet with her sister Jenny at the mental hospital and needs a 24-hour furlough for her. Once Irving provides it, Abbie goes to see her sister. Jenny isn't interested until Abbie describes how Katrina told her to find a Sin Eater, and Jenny warns her that they have to work fast.
Ichabod wakes up in an underground chamber and finds several men waiting for him to regain consciousness. Their leader sits down, holding a ledger, and apologizes for abducting Ichabod. Ichabod notices his cufflinks monogrammed "JR" and notices his family resemblance to Edward Rutledge, the youngest signatory to the Declaration of Independence. The Englishman also takes in the various hexes painted on the walls and the fact that Rutledge has removed a ring, and realizes that he's a Freemason. Rutledge concedes that he is and wonders if Ichabod is who he claims. When Ichabod wonders why he wouldn't be, Rutledge points out that there are demons and shapeshifters moving among them. Opening the ledger, Rutledge recites "Order into chaos" in Latin, and asks Ichabod when he first heard it. Ichabod explains that he first heard the phrase from Arthur Bernard, a freed slave.
Ichabod is still with the British forces in the Americas and accompanies Colonel Tarleton to Arthur's house. Tarleton is looking for a Revolutionary who is distributing pamphlets under the alias of "Cicero." Arthur denies knowing anything about Cicero, so Tarleton slaps him and calls in Ichabod, ordering him to wring a confession from Arthur. A local Quaker nurse--Katrina--comes in and requests an audience. She is furious that they have injured Arthur and orders Ichabod to let her treat the prisoner's injuries. Arthur assures her that she's in good hands and Ichabod glances nervously at Tarleton. Katrina realizes that Ichabod is feeling the qualms of conscience and leaves.
Abbie takes Jenny to the archive and they go over the records looking for a reference to a Sin Eater. Jenny explains that every culture has a legend of a Sin Eater, a person who can consume another person's evil. Among the many strange phenomena that she and Corbin investigated were reports of a Sin Eater visiting death row prisoners. Each one said afterward that they were sanctified. Abbie remembers Katrina saying that Ichabod must be sanctified Meanwhile, Jenny tells her sister that the Sin Eater she was tracking disappeared two years ago.
Ichabod finally orders Tarleton's man to stop beating Arthur and sends him away. Arthur asks Ichabod if he would sacrifice a man to do his job, and warns that demons are disguised as men, moving among them and turning brother against brother. The prisoner asks Ichabod to join him, but Ichabod assumes that he's delirious.
Rutledge asks Ichabod what happened after he failed to force Arthur to confess.
Tarleton summons Ichabod to watch the execution of three Revolutionaries preaching out against the Crown. As they're hung, Katrina comforts one of the dead men's sons. She looks accusingly at Ichabod, who hesitantly approaches Tarleton and suggests that their approaching is breeding more rebels. Tarleton warns Ichabod not to give him the opportunity to question his loyalty, and Ichabod insists that he is loyal to the King. As Tarleton walks away, Ichabod is shocked to see his face briefly take on a demonic cast.
Later, Ichabod meets Katrina in the forest and insists that the execution wasn't his doing. Katrina warns him that he is just as guilty by aiding Tarleton as if he had pulled the lever himself. Ichabod asks her about the demon face that he saw and Katrina tells him that his conscience has led him to see the truth, and that what he chooses to accept will become his destiny. He admits that he's heard rumors of a secret supernatural war, and Katrina realizes that Ichabod is the one that "they" foretold. He has the power to bear witness. Before she can explain further, two Redcoats on patrol ride toward them and Katrina prepares to leave. She tells Ichabod that evil triumphs when good men do nothing, and assures him that he's a good man.
As Abbie grows increasingly frustrated, Jenny wonders about her sister's feelings for Ichabod. Abbie explains that after she lost first Jenny and then Corbin, Ichabod came into her life right after Corbin was murdered. He gave her a purpose that she could understand. When Jenny notes that Katrina didn't give them much information to stop Ichabod from becoming a dead man, Abbie gets an idea and goes over the visitor's logs of the death-row prisoners. Each one was visited by a man using the name of a dead inmate. They check the last name and then trace it to an apartment in Hartford, CT.
After running a background check, the sisters go to the man's apartment and knock. The man inside reluctantly lets them in when Abbie threatens to charge him with identity theft. She says that they know that his real name is Henry Parrish, and asks for his help finding Ichabod. Henry refuses, saying that he doesn't eat sins anymore. The evil that he consumed threatened to overwhelm him, leaving nothing behind. Jenny tells him that they both know what it's like to live with something that no one else has, and Abbie tells Henry that he has a gift that he shouldn't waste. She explains about the Horseman and Revelation, and Henry realizes that the Horseman--a force of pure sin--is connected to Ichabod by a blood tie. When they ask if he can find Ichabod, Henry admits that he could use Abbie's connection to the other Witness to locate the missing man, but he refuses. Abbie grabs him, furious, and Henry gets a series of visions. They lead him to a door marked with a Freemason symbol, somewhere deep underground. Henry tells them what he's seen but refuses to do anything else to help them.
The sisters return to Sleepy Hollow and Abbie leads Jenny into the tunnels beneath the he city, left over from the Revolutionary War. They then start searching for the door from Henry's vision.
When Rutledge asks Ichabod what happened next, he says that he went to Arthur's home and his sins were revealed.
Tarleton is waiting for Ichabod and tells him that he's failed to find the identity of Cicero. The colonel offers Ichabod one last chance to make amends by taking Arthur out into the forest and shooting him. Ichabod has no choice but to agree and leads Arthur out into the woods. Arthur tells him that he has a gift and that if he commits murder then he is opening his heart up to evil. Ichabod ignores him and finally tells him to march ahead. He raises his gun and fires... just grazing Arthur's shoulder. Arthur warns him that the life he knew will never return, and tells him to go to Katrina so she can lead him to Washington and Ichabod's destiny. He gives Ichabod the code phrase and tells him to recite it to Katrina so she'll know which side he has chosen.
As Arthur starts to escape, Tarleton arrives and shoots him down. Furious, Ichabod draws his sword and charges the colonel, stabbing him in the stomach. However, Tarleton reverts to his demon form and knocks Ichabod back through the air. As he prepares to kill him, a Redcoat patrol rides by. Forced to retreat, the Tarleton demon runs off into the woods. Ichabod manages to stagger out of the forest and make his way to Katrina's home. When she opens the door, he tells her the code phrase and collapses.
Ichabod confesses that he sinned because he didn't act quickly enough to save Arthur. Having confirmed everything that Ichabod described against the ledger, Rutledge is satisfied that Ichabod is who he claims. He and the other Freemasons offer Ichabod their trust. When Ichabod wonders who wrote the ledger, Rutledge explains that it came from Katrina. Katrina's coven and the Freemasons were allies, but Katrina hid Ichabod's body where no one else could find it. Ichabod realizes that his wife hid him from the Freemasons, and Rutledge says that they must kill Ichabod for the greater good. If Katrina hadn't protected Ichabod, he would be long dead and the Horseman with him. Rutledge takes out a box and puts it before Ichabod, and says that he knows what he has to do.
As Abbie and Jenny find the door from Henry's vision, two Freemasons confront them and order them to surrender. Abbie refuses to back down, pointing out that she can have backup there in a matter of minutes. She demands to see Ichabod and the Freemasons take her into the chamber. Ichabod asks Rutledge to give him and Abbie a minute alone. Once everyone leaves, Ichabod says that if he kills himself then it will destroy the Horseman as well. Abbie insists that there's another way if she can convince Henry to help, but Ichabod says that with nightfall coming, the Horseman will ride again and it will be too late. He take out a bottle of poison from Rutledge's bod and says that he has to do it so that they can avert the Apocalypse. Abbie insists that there has to be another way, but Ichabod tells her that there isn't.
Ichabod asks Abbie to leave, but she refuses to let another friend die alone. He drinks the poison and starts to collapse... and Henry arrives. He orders Abbie out and then drives a knife into Ichabod's palm, letting the blood pool on the table. Henry tastes it and warns Ichabod that as long as he carries sin in his heart, the Horseman will feed on it. Ichabod says that his sin is that he couldn't save Arthur, and Henry tells him to summon the face of his friend. Ichabod concentrates and sees Arthur take Henry's place, and tells him that he did everything he could to save him but he failed. Arthur assures him that his death led Ichabod to his destiny, saving his soul, and tells him to forgive himself. If he doesn't, the Horseman will continue feeding on Ichabod's regret. When Ichabod hesitates, Arthur tells him that he and Abbie will triumph. Ichabod finally recites the ritual, casting out sin from his heart and telling death to leave him.
The cellar shakes as the pool of buddle separates into two puddles: one of Ichabod's and one of the Horseman's. Henry dips some bread into the blood and then drinks it, taking on Ichabod's sin. The shaking stops and Ichabod realizes that he can no longer feel the blood tie to the Horseman. Abbie and the others come in and Henry tells them that Ichabod is sanctified. She hugs Ichabod and he admits that she was right: there always is another way. The sun sets and Henry warns that the Horseman will ride again... and come for Ichabod. Rutledge says that they must make preparations and Ichabod assures the others that they'll be ready.
As the sun goes down, the Horseman goes to the cave where Ichabod's body was kept. He kneels and examines the dirt with care.