Rome, 1659. Months after the plague has ravaged Rome, men are still dying in unnatural numbers, and rumour has it that their corpses do not decay as they should. The Papal authorities commission prosecutor Stefano Bracchi to investigate, telling him he will need considerable mettle to reach the truth.

To the west of the Tiber, Girolama and her female friends are at work, helping other women with childbirths and foretelling their futures. Elsewhere in the city, a young wife, Anna, must find a way to escape her abusive husband. But in a city made by men for men, there are no easy paths out.

Stefano's investigation at the Tor di Nona prison will introduce him to horror, magic and an astonishing cast of characters. He will be left wondering if certain deeds should remain forever unpunished...

The Book of Secrets is inspired by real events that took place in 17th century Italy.