France, 1565. Charles IX reigns with an aging Nostradamus as his advisor, but unrest is afoot in the land. The Black Plague, believed to be under control, rears its head anew. Superstition vies with newly born science in the people's hearts and minds. Through a countryside riven by religious and political rivalries travel Nostradamus' three young disciples, Arthus Trivium, Angelica Obscura, and Angulus Dante, solving mysteries with wits, weapons, and the erudition their master has imparted. But soon they are drawn into the web of a well-laid plot against Nostradamus' family, which may threaten the life of the king himself.

The Demon Zagan, Lord of All Things, and his undead minions have captured the young Charles IX, King of France, as well as Nostradamus and his family and are holding them hostage—but who let them into Nostradamus' home? None other than his mentor, Scaliger, long believed dead. Consumed by envy for his former protégé, the scholar now serves Zagan, who seeks an orb created by the earliest magicians to defend the earth from the realm of the dead. It's up to Nostradamus' three young disciples, Arthus Trivium, Angelica Obscura, and Angulus Dante, to rescue their master from dire peril!

When Nostradamus entrusts his disciple Arthus with training his son Cesar, he believes their mission a simple one: investigate a village where a rain of blood has been reported. But upon reaching Cucuron to find all the menfolk missing, Arthus realizes the adventure is more than he bargained for. Meanwhile, in Paris searching for a young girl who's disappeared, Angulus and Angelica come upon a mysterious canvas in the workshop of a famous painter that seems to lead Angelica to another world. The stakes rise for all three disciples as they find themselves separated, each facing their own perils.

Book Four finds our hero, Arthus Trivium, trapped with Cesar, his Master Nostradamus' son, in a burning church presided over by Melusine, a witch with a serpent's tail. She's out to bring justice and wreak vengeance on a village torn by the rape and murder of several young women. But she isn't the only villain with a noble cause. In an eldritch realm that Angelica and Angulus have visited by means of a sleeping draught, Arthus' fellow disciples face a powerful sorceress planning no less than to wipe out all men. And over the centuries, unseen, she's built up quite an army...