An old nemesis of Alden's arrives in Salem with secrets that could destroy him. Meanwhile, Mary loses her grip on Mercy.

Romantic yearnings between Mary and Alden heighten as Cotton deals with a unique accusation in the trials. Meanwhile, a powerful witch hunter makes his way towards Salem.

Increase Mather makes it his first order of business to catch a real witch, and starts by pinpointing a prominent figure from Salem’s most sinful district. Mary worries that Increase will detect that his old friend George is under a spell and enlists the help of Isaac to deter Increase from uncovering the truth. Meanwhile, accusations within Salem intensify and Cotton must deal with a painful turn of events – and Anne’s suspicions of her father reach a fever pitch.

Salem sees a second death since Increase's arrival in town, and Mary struggles to get George back under her control. Mercy and her acolytes flex their growing power while Increase grows closer with Isaac, putting Isaac’s loyalty to Mary in question.

Increase gets closer to understanding who really runs things in Salem; at the same time, Anne finds herself in danger, and in need of Alden's help, while investigating a mystery.

Alden’s trial begins, triggering a chain of events that breaks nearly every remaining allegiance left in Salem. While Mary arms the Malum for the Grand Rite, the coven elders urge her to use Alden as the final sacrifice. Increase seizes Mercy’s acolytes for information to use against Alden – an act that carries more consequences than anyone anticipated.

Alden comes to learn Mary's biggest secret.