Frank Thorney risks being disinherited for having married Winifred, who is pregnant; what he doesn't know is that his master, Sir Arthur, is the father of the child.
Meanwhile, the Thorney family is in financial difficulties: Frank must marry Susan Carter for her marriage portion, which will save the Thorney estate from having to be sold. He denies having married Winifred, producing a letter of verification from Sir Arthur, and marries Susan bigamously.
Beaten by Old Banks as she gathers firewood, and abused by Cuddy Banks and his morris-dancing friends, Elizabeth Sawyer longs for magical power to take her revenge. The devil appears to her in the form of a black dog and induces her to give away her soul in return for his services.
Cuddy seeks her help in his amorous pursuit of Kate Carter, and she arranges an assignation for him: since the dog cannot kill Old Banks, Cuddy's misfortunes will be a way of getting at his father.
Cuddy keeps his appointment, but the dog leads him not to Kate but to a spirit in her shape. He gets a ducking, but makes friends with the dog and asks him to appear in the morris dance. The dog obliges, and bewitches the fiddler's instrument, so there is no music for the dance until Cuddy gets the dog to play it himself.
The melancholy Frank tries to abscond with the cross-dressed Winifred, but he has difficulty getting rid of Susan. When Winifred goes ahead, they meet the dog, which induces murderous thoughts in him. He stabs Susan, then wounds himself and ties himself to a tree with the dog's unseen assistance.
When found, he accuses Warbeck and Somerton of the assault, and they are arrested.
Mother Sawyer is blamed for an outbreak of cattle blight, and for widespread sexual misconduct by the local women. She protests her innocence when questioned by a justice, and calls attention to abuses committed by courtiers and citizens; but once alone she suckles the dog with her blood and makes mischief.
Anne Ratcliffe, with whom she has a minor quarrel, is driven mad and kills herself. Mother Sawyer is arrested.
Frank is visited in his sick-bed first by Susan's ghost, then by Winifred. He confesses the murder to Winifred. When Katherine finds a bloody knife in his pocket, Winifred confirms the accusation and he is arrested.
The dog appears to Mother Sawyer in prison, now with white fur rather than black, and makes it clear that he has no intention of helping her further: she is already damned, so he has got what he wants.
He also takes his leave of Cuddy Banks, who is spiritual small fry and not worth bothering with; corruption in high places will be more rewarding.
Somerton and Warbeck are released.
The penitent Frank and the impenitent Mother Sawyer are hanged.
Sir Arthur is ordered by the court to pay Winifred a thousand marks.
Synopsis reproduced with permission from Martin Wiggins, British Drama, 1533-1642: A Catalogue (Oxford, 2012- ).
Image: Harriet Walter as Mother Sawyer in our production of The Witch of Edmonton in 1981.