In the Middle Ages: the knight Thibault de Malmort brings back from a crusade an ancient cursed grimoire, which belonged to a cult worshipping Satan. By not following the spellbook reading rule, the knight, his wife Adeline and his servant Ugatorus were cursed through the centuries. Nowadays: One of the knight's descendants throws a Halloween party in Malmort Castle. The guests inadvertently discover the old grimoire and manage to open it. Little do they know that the two guardians of the castle are Adeline and Ugatorus. They must perform a ritual and offer eight hearts as a sacrifice in order to make the Knight of Death reappear and free themselves from the ancestral curse, while offering Satan a son so that his reign on Earth will be complete. The guests will become prey for Adeline and Ugatorus, who are determined to get the eight hearts...