[Read a review of “A Discovery of Witches” and an interview with one of its stars.]

“It’s a very character-driven story, which is why I’m glad it ended up with Sundance,” Harkness said. “It means we don’t have to blow up so much stuff and have so much fake blood.” As executive producer of the show, Harkness had a hand in everything from the casting to the edits. She has been busy promoting both the show and “Time’s Convert.” Harkness gives a lot of interviews in hotel rooms — which may be why her publicist stipulated that this one take place at the Langham Huntington, even though the author lives less than two miles away. In any case, Harkness, who arrived in jeans and well-worn cowboy boots, her blonde hair staticky from the Santa Ana winds, fairly radiated spontaneity and sincerity. Maybe it was the wine.

She was, for example, expansive on the subject of new projects, a topic many writers would rather submit to a tax return than discuss. All Souls groupies will be happy to hear she is now 200 pages into a book about Matthew grappling with the forces of religious radicalism in 16th-century Europe. She recently returned from a three-week cruise around New Zealand to research another book about Matthew’s nephew, the beloved soldier and mercenary Gallowglass. A deep dive into the history of witchcraft is also in the works.

Harkness is descended from a witch — or at least a woman hanged in Salem for allegedly practicing witchcraft. The supernatural seized her imagination at a young age. “I can still see ‘The Witch of Blackbird Pond’ on the shelves of the Horsham library,” she said. Horsham, a suburb of Philadelphia, is not a bad place to grow up if you’re interested in history, another early passion of hers. There were family picnics at battlefields, tours of historic houses. When she was 8, her father, the manager of a paint store, and her mother, who worked as a secretary, took Harkness and her younger brother on a trip to England — sparking a lifelong interest in Elizabethan history.

She went to college at Mount Holyoke, where she designed her own major, in Renaissance Studies. A class called “Magic, Knowledge and the Pursuit of Power in the Renaissance” was transformative: “It was like somebody had taken a can opener to my brain and peeled off the lid. The teacher opened up the class by asking, ‘How do you know what you think you know?’ I’ve never stopped asking that question.”