Philippe de Montfaucon, a French marquis, is called back to his ancestral vineyard in the rural countryside due to a poor harvest. His concerned wife, Catherine, and their children accompany him, despite his insistence that they remain in Paris. Upon their arrival at the estate, Catherine notices a strange and unsettling atmosphere surrounding the place and the local townspeople. She becomes particularly uneasy around two enigmatic siblings, Christian and Odile de Caray, who seem to possess an unusual influence over Philippe and are shrouded in mystery. As Catherine explores the estate and its environs, disturbing elements come to light, including ominous rituals that seem rooted in ancient traditions.

Undeterred by her husband's dismissive reassurances, Catherine delves deeper into the history of the estate and its relation to the locals' strange beliefs. Her search brings her into conflict with those intent on maintaining the old ways and preserving some dark secret that seems integral to the prosperity of the vineyard and community. The tension between preserving tradition and breaking its hold surfaces as Catherine struggles to ensure her family's safety amidst growing threats and an ever-increasing sense of menace from those around them. With her husband seemingly complicit in these unsettling happenings, Catherine is caught in a battle against time to uncover the truth before it is too late for her family.