During a social evening at Christopher Hatton's country estate, Mordelaine, his son Barney has a romantic tryst with Dilys Helmar.
But the next day, Barney discovers that his mother's jewels have been purloined by her husband, who has spent all night gambling with Dilys' father Nick. Barney arrives just in time to see Mordelaine lost on a single unlucky throw of the dice.
The Hattons are forced to move to a cottage in a nearby village. One day, while his horse is shod by blacksmith Bob Wicks, Barney sees some villagers tormenting a young woman, whom he rescues. She is Jassy Woodroffe, considered a witch because of her mother's gypsy blood (her father, Tom Woodroffe, is a respected village elder) and her gift of second sight.
Mrs Hatton hires Jassy as a domestic servant, over and above the maid Meggie's suspicions. Tom Woodroffe breaks up an altercation between Bob Wicks and his daughter Lindy, but Wicks' brutal whipping has struck her dumb.
At Mordelaine, its new owner Nick allows Christopher credit to continue gambling - but Christopher is caught cheating. Shamed, he goes upstairs and kills himself. After discovering the body, Nick finds his wife in the arms of a lover. After she reveals the affair has been going on for months, he agrees to a divorce.
At a stormy village meeting, Tom Woodroffe assembles a crowd to march on their landlord to ask for better pay and conditions. They are confronted on the doorstep by a drunken Nick. (Back in the village, Jassy senses that something horrible is happening to her father and implores Barney to do something). Nick and Tom struggle, Nick's shotgun goes off, and Tom is fatally wounded. (Jassy screams, and tells Barney that he's too late).
Jassy and Barney become increasingly close - too close for Mrs Hatton, who asks her to leave, though with an excellent reference that manages to secure her a job at a young ladies' finishing school. There, she meets and makes friends with Dilys after catching her sneaking out one night for a romantic tryst - but she is blamed for Dilys' disappearance and sacked.
Dilys takes Jassy to Mordelaine and introduces her to her father as her friend. Nick is convinced that he's heard the name Woodroffe before, and Jassy reminds him that it was the name of her father. Nick apologises for his actions, blaming drunkenness.
Dilys and Jassy go to see Barney. To Jassy's chagrin, the romance between Dilys and Barney rekindles, even though Jassy knows that Dilys has also been seeing Stephen Fennell. Jassy plays chess with Nick, and he offers her the job of running Mordelaine. Jassy restructures of the staff, sacking some and promoting others. Mrs Wicks persuades her to take on Lindy, who turns out to be an excellent worker despite her silence.
One day, Jassy catches Dilys and Stephen together (unknown to them), and is shocked to hear later the same day that Barney has proposed to her. In a rage, Nick horsewhips Dilys, who runs out into the arms and carriage of Stephen. Barney goes to see Stephen and finds that he and Dilys are engaged.
Meanwhile, Nick makes his intentions known towards Jassy, eventually proposing marriage. She refuses, but reconsiders when he agrees to give her Mordelaine as a wedding gift. They marry, but Jassy insists on living separately. In a fury, Nick goes out riding and has an accident. Lindy finds him and summons Jassy.
He is brought back to Mordelaine, where the doctor prescribes a strict diet and no alcohol, which Jassy enforces, even though Nick is increasingly violent towards her. When Jassy goes to visit Dilys and Stephen, and Lindy decides to poison Nick for what he's done to Jassy, slipping rat poison into a bottle of wine.
Nick's murder is sensed by Jassy, who cries out that he's dead. Stephen thinks that she murdered him, and has her arrested along with Lindy. At the trial, despite Jassy's alibi, the pair are found guilty, but the shock goads Lindy into speech. She confesses to the murder, exonerates Jassy, and drops dead. Jassy signs over Mordelaine to Barney, its rightful heir, and the reunited couple kiss.
