Seventeen-year-old Ismay, having escaped from her husband, is ready to take revenge on all the men in the world for the cruelty she experienced. And amazingly, it’s as if the heavens themselves are responding to the voice of her anger. In the abbey that gave her shelter, all sorts of methods of killing are comprehended day and night. The nuns' lives are dedicated to the ancient Celtic deity, who took the guise of a Christian saint. At the right time, the Dark God of Death marks the victim with a distinctive sign so that the hand of the killer sent by the monastery will strike an unmistakable blow.