Volume 4 of the "Luzia" series. Marburg 1612 - Lukas von Wegener, a sought-after astrologer and polymath, travels to Thuringia with his wife Luzia. In the town of Mühlhausen, a travelling medic has predicted a plague epidemic, and Lukas is to refute him with a horoscope. Apocalyptic conditions welcome them, the people are rebellious and vicious. To make matters worse, Luzia is recognised as a former thief, but she also receives unexpected help. The city authorities are convinced that the Medicus is causing the plague through witchcraft. The only chance to save him from the stake seems to be an antidote, the imminent discovery of which Luke hastily announces. Too rashly, as soon becomes clear, for the Duke's envoy demands a panacea from Luke - the Philosopher's Stone!
