Ars Magica
 Spain, early 17th century. A woman is found lifeless in Santesteban. All points to a murder committed by the Devil and its followers. The region is being scourged for months by the sorcerers, even if the precedent year eleven people were burned alive in a sorcery trial. The people are scared. To appease them the Santo Oficio decides to promote a grace edict to forgive those who admit their agreements with the Devil. The severe inquisitor Alonso de Salazar y Frías is in charge to apply the edict by covering the region. But what nobody knows is that Salazar doesn't't trust anymore in sorcery or spells and, even worst, he doesn't trust in the Devil any more, because he has lost his faith. To reveal the mystery of the witches, Salazar will use the anatomy studies from Leonardo da Vinci, forensic technics he learned in Rome, apothecary knowledge to analyse magical ointments... he finally will base his investigation on verifiable facts to establish factual truths instead of suppositions. Meanwhile, a young woman called Mayo from Labastide-d'Armagnac, who was, following her birth statements, the bastard daughter of the Devil and a mortal woman, travels selling spells. Mayo lost her female companion because this one was arrested during the last auto-da-fé, even if she wasn't condemned. To find her, Mayo decides to follow the steps of Salazar, whom she protects with her spells, even if he doesn't suspect anything about her beneficial actions. During their journey, both will face the diabolical powers which will obstruct their plans, the lack of faith and the death of those they love.