In medieval Tallinn, a famous knight who is freed from the pirates of the Baltic Sea is murdered. The hero's head is cut off and his mouth is stuffed with coins. The gold chain he bought the same day is missing. The bailiff orders Melchior, an apothecary, to investigate the crime. The clever young man discovers that the slain was looking for a mysterious "Tallinn prisoner" and the traces lead to the Dominican monastery. A fabulous sequence of bloodwork is unleashed - anyone who comes into contact with this secret is in danger of dying.

In the middle of the night, a drunk town guard happens to meet the daughter of a rich merchant… who drowned herself into a well 10 years ago. Soon after the town guard falls dead from the tower. This is followed by two other suspicious deaths. Doubting the existence of the ghost, Melchior has a hunch that these ‘accidents’ are part of a heinous crime. Tracking down the killer, his path will cross with heretics, old feuds and dark family secrets.

Melchior’s bride Keterlyn happens to witness an attack on a young man. The victim, who has lost his memory, does not know who he is and how he ended up in a Tallinn. A ring found at the scene leads Melchior to the trail of the nocturnal brotherhood, questions are also raised by the troupe of freaks who performed on fair day. Ominous signs suggest that not only is the stranger recovering from a murder attempt at risk, but Melchior and Keterlyn as well. At the same time, an inquisitor known as a ruthless witch hunter arrives in town. Melchior's ability to "speak to the dead" and to notice invisible traces of murder have raised the suspicion that he may be a dangerous heretic. And the place of the enemy of the church is at the stake…