It is the year of the Great Conjunction, when the two most powerful planets, Jupiter and Saturn, align—an astrological phenomenon that occurs once every thousand years and heralds the death of one age and the dawn of another. The streets of London are abuzz with predictions of horrific events to come, possibly even the death of Queen Elizabeth.

When several of the queen's maids are found dead, rumours of black magic abound. Elizabeth calls upon her personal astrologer, John Dee, and Giordano Bruno to solve the crimes. While Dee turns to a mysterious medium claiming knowledge of the murders, Bruno fears that something far more sinister is at work. But even as the climate of fear at the palace intensifies, the queen refuses to believe that the killer could be someone within her own court.

Bruno must play a dangerous game: Can he allow the plot to progress far enough to give the queen the proof she needs without putting her, England, or himself in danger?