In the heart of 15th-century Tallinn, a series of horrific murders shakes the city as the bodies of builders are discovered near the construction site of St. Olav's Church. The flowing blood threatens to turn the sacred project into a mysterious curse hanging over everyone. Amidst rumors of demons roaming at night and conspiracies brewing in the shadows, the pharmacist Melchior stands out with his keen mind and rare ability to uncover hidden threads. He possesses neither a sword nor an army, but rather sharp logic and meticulous observation that lead him to the secrets of both the church and the city. Melchior's journey is not just a hunt for a serial killer, but a dive into the depths of tense Tallinn, where ambitions for wealth intertwine with religious and commercial conflicts. This novel combines detective suspense with a dark historical atmosphere, offering a captivating adventure brimming with mystery and intelligence amidst a perilous medieval world.