Plot summary
Ichabod and Abbie learn that a powerful warlock who oversaw the Salem witch trials has escaped from purgatory and is attempting to change the past using the Grand Grimoire. Katrina reveals that the man's hatred of witches stems from a failed love affair with one, and that she and her coven were able to banish him using their combined power. They confront the warlock, but he overpowers them and escapes. Katrina unexpectedly leaves the case to Ichabod and Abbie, forcing them to turn to Irving. Using electricity (as warlocks are weak to the elements), they weaken him, but he escapes once again. During an ensuing manhunt, Irving finds the man and kills him, before giving the Grimoire to Henry. Katrina becomes increasingly obsessed with black magic, which she witnessed the warlock using earlier.
Credits
Adapted from Wikipedia contributors, Sleepy Hollow season 2. HTML formatting and reference markers removed.