SPOILERS: 1609, Basque Country (north to Spain). In a land full of pagan legends and ancient traditions, Judge Rostegui belonging the Spanish Inquisition is chosen by king Felipe III to be sent with a notary and a group of soldiers to purify all the region, traveling town by town to burn any woman with signs to be a witch. Obsessed to disclose the secrets of the infamous Sabbat (a theoretical feast where the witches make a ritual not only to summon The Devil, but to promise loyalty and mate with him) and denied to believe that it doesn't exists in his absolute conviction that it's for real, Rostegui arrives to an unnamed coastal village with no men (after they are sailors navigating by the sea) where five girls in their 20 years old are arrested: Ana, Olaia, María, Maider and the still teen Katalin. Not knowing the reason for the arrest, the girls are submitted to a hard interrogatory including torture to get the confession about they are witches and how it's the ritual of Sabbat. After to learn horrified how Maider is shaved in her head to bald and severely tortured in her body looking for the Satan's seal (a supposedly secret and invisible mark left in the body of a witch that it leaves this part of her body insensitive to any pain), a scary Ana convinces to the rest for inventing all the Sabbat for Rostegui, explaining it as long as be possible, hoping that their fathers comeback in a week during the full moon tide. Discovering the special interest of Rostegui on her, and mixing Basque ancient traditions with popular songs, Ana and the others will use all their imagination to save their lives. But Rostegui starts to suspect if Ana and the rest are in true the witches that suddenly they claim to be and their intention to celebrate Sabbat.