This is the opener in a new series featuring Beatrice Scarlet, a 17th century female apothecary. Female apothecaries, of course, were virtually unheard of at that time, but Beatrice has been nurtured by her newly deceased father, a very experienced London apothecary who taught her everything he knows.
Unfortunately Beatrice's mother has recently died leaving her still a child, in possession of a house and business in London. When her cousin Sarah, a widow from Birmingham, offers to take her in, she has to accept, not realising that Sarah will take all her inheritance, supposedly for her up keeping. Beatrice becomes the household drudge, and also has to avoid the amorous advances of Sarah's unpleasant son, Jeremy. Sarah's family are strict Calvinists, and life for Beatrice would be unbearable were it not for the friendly glances bestowed on her at church by Francis, the son of the pastor. Several years pass as Beatrice's situation worsens, with Cousin Sarah trying to force her to marry the odious Jeremy. Francis sees what is going on and asks her to marry him.
Scarcely knowing one another, they set sail for New England, where Francis has been offered the post of pastor in a small village, Sutton, in New Hampshire. There they live happily for a year or two, despite Beatrice secretly not going along with Francis' extreme religious convictions. Her happiness blossoms when she gives birth to a son, Noah. When Noah is a toddler, bad things start to happen in Sutton. Francis' and Scarlet's pigs are found dead one morning, with no obvious injury or illness. The local women begin to talk about the possibility of Widow Belknap [who lives on her own in a remote part of the village], being a witch.
The events in the narrative occur several years after the Salem witch trials; so Scarlet is horrified when Francis, who agrees with her that Salem was mass hysteria, expresses his belief that Satan could be using unspecified agents to destroy the village. More animals suffer unexplained deaths and a mysterious and spooky stranger, Jonathan Shooks [who seems to be attracted to Scarlet], offers to negotiate with the local demon, who he claims is acting as Satan's agent. Scarlet is absolutely convinced that the terrible events, as they become more frequent, and move on to human beings, are caused by a human agent, but Francis disagrees with her, although he thinks Jonathan Shooks is evil.
The human deaths get more and more horrific. The pace quickens to a terrible conclusion.
The horror element of the story to me is lessened by what seems to be the matter-of-fact way the villagers accept events which you would think would drive most of them insane. Scarlet I am sure will survive to fight another day.