Plot

Merricat, Constance and their Uncle Julian live in isolation after experiencing a family tragedy six years earlier. When cousin Charles arrives to steal the family fortune, he also threatens a dark secret they've been hiding.

After a family tragedy involving arsenic 6 years ago, the remaining 3 still live in the castle isolated from the nearby village. 18 y.o. Merricat shops in the village weekly but it's unpleasant the way many villagers treat her. Her magical spells don't seem to protect her. Her older sister Constance and uncle Julian never leave the property. The sisters' cousin Charles arrives unannounced, not really to meet the family but rather for the money in the big safe. Chaos ensues.—Scott Filtenborg

Set in a rural New England town in the early 1960s, 18-year-old Mary Katherine "Merricat" Blackwood lives on the family estate with her older sister Constance and their ailing uncle Julian. Constance has not left the house for six years ever since she was tried and acquitted of the death of her parents by poisoning. Every Tuesday, Merricat goes to the village to shop for food and groceries while the villagers harass her. Merricat practices her own brand of protective magic witchcraft by burying articles of power in the ground that in her belief is to keep evil forces at bay and protect Constance.

Constance sees only a single family friend, Helen Clarke, who visits the house every Wednesday for tea. Helen tries to convince Constance that she should rejoin the outside world. This enrages and terrifies Merricat, who creates magic to prevent Constance from leaving. On Thursday, Constance sends Merricat on an errand to town. Merricat is distressed at the thought of going into town on the wrong day and has no time to check her magical safeguards. When she returns, she finds all her wards have been unearthed. Before she can warn her sister, she is introduced to their estranged cousin, Charles.

Over the next few days, Charles attempts to lure Constance away with the promise of seeing the world while setting his sights on the family fortune, a hoard of cash that is locked in a safe. Constance is charmed and subservient toward him. However, Charles behaves condescendingly to Julian and taunts Merricat with the idea of stealing her sister. Merricat retaliates by casting magical spells on Charles, vandalizing his room and belongings, and speaking to him only in descriptions of poisonous plants. When Charles threatens to punish her, Merricat throws everything on his desk, including his lit pipe, into a wastebasket. Charles beats her until he discovers that his room is on fire.

The fire department arrives, along with the villagers, who call to let the house burn. Constance and Merricat hide downstairs as the fire is extinguished. The villagers rush into the house and vandalize it. The mob seems ready to attack the sisters, but Helen Clarke's husband announces that Uncle Julian has died of smoke inhalation. The mob disperses, and the sisters take refuge in the woods.

The following morning, the sisters return home to their fire damage house and barricade the doors and windows. With the upper floors destroyed, the remains resemble a turreted castle. Merricat announces that she intends to poison the whole village; Constance reveals that this is what Merricat did once before to their parents and expresses gratitude that Merricat saved her from their wicked father. The villagers leave gifts of food at their door and apologize for destroying their property, but the sisters never respond. Charles returns, begging Constance to let him in. When they remain silent, Charles enters the house by force and attacks Constance. Merricat bludgeons him to death with a snow globe, and they bury him in the garden.

In the present day sometime later, the sisters are cleaning what remains of their burned-out house when two village children arrive to taunt them. Merricat steps outside, and the children flee in fear for some unknown reason. Constance tells Merricat that she loves her, and Merricat, for the first time in the film, smiles.