The following version of the book was used to create this study guide: Galchen, Rivka. Everyone Knows Your Mother Is a Witch. Farrar, Straus, and Giroux., New York, NY, 2021. Kindle AZW file.

Katharina Kepler is a widow living a normal live in Leonberg. Her son Christoph lives nearby with his wife Gertie. Her daughter Greta lives in a neighboring town with her husband Pastor Binder. Her son Hans, who is a famous astrologer and the Imperial Mathematician, lives in Linz with his second wife, Susanna. Katharina has managed to become friends with a reclusive neighbor, Simon. When Katharina is summoned to the office of Govern Lukas Einhorn, she expects he is going to ask her to request some astrological document from Hans. What she discovers is that an unhealthy and unhappy woman named Ursula Reinbold claims Katharina is a witch and is the cause of her health issues. Katharina points out that she should have a male guardian with her if she is being questioned and Einhorn, apparently realizing he has made a legal mistake, tells her to forget it happened. Ursula continues to spread the rumors, however, and Katharina turns to Christoph and Gertie for advice.

Gertie is an avid reader of pamphlets and believes all the stories are true. She has read about a woman convicted of witchcraft, and the judges questioned why she never objected to being called a witch. With this in mind, Christoph accompanies Katharina to file a claim of slander against Ursula. The problem is that this makes Einhorn's mistake a matter of public record, and he ties this case up while allowing the witchcraft trial to proceed. Katharina cannot read and she turns to Simon to help her create a true account of events.

Katharina travels to Linz where she stays with Hans for awhile, then returns to Leonberg, hoping the rumors would have blown over. They do not, and the trial continues with many coming forward with “proof” of Katharina's witchcraft. Eventually, Katharina is arrested and held for weeks in brutal conditions. When the trial wraps up, Katharina is found innocent, but her situation is forever changed. Simon recounts the events that happen in the years after the trial. Einhorn and Ursula's family make very specific and brutal threats, meaning Katharina can never return to Leonberg. She settles down with Greta, but Pastor Binder is not welcoming. Almost all her money has been spent during the trial. Katharina is without means to do anything differently. She dies in her sleep not long after the trial.

More than a decade later, Simon encounters Hans's widow, Susanna at a book festival. Hans is trying to sell a manuscript about a widow who faces unjust accusations – clearly his version of Katharina's story. Susanna is trying to sell a manuscript Hans wrote about a woman who learns from ancient spirits how to travel to the moon, and uses the information so her son can have that experience. That manuscript had been brought up during the trial as “proof” that Katharina was a witch. The new version has footnotes in which Hans repeatedly explained it is a work of fiction.

Simon recounts the fate of others, including that Pastor Binder was murdered by marauding soldiers, Christoph became a judge, and Greta married a poet after her husband's death. The one thing he cannot answer is whether Katharina was unjustly accused.