Commissioner Sumara and his new colleague Šímová investigate an attempted ritual murder that has some connection to archaeological excavations at the Podlažice Monastery.

Members of Schola Gregoriana Pragensis appear in a small roles of Benedictine monks singing Gregorian chant.

The series is sometimes compared to The Da Vinci Code, and Dr. Runa to Robert Langdon.

Dr. Runa comes up with a code by which the killer searches for victims (related to the numbers in the pentagram), and it turns out that his daughter, who has just disappeared, is in danger.

The solution to the mystery is mystical and related to the Codex Gigas book, the magic square 6×6, the Porta coeli Convent and the murder of Wenceslas III in 1306.