"When the moon is at the full"
Popular superstition ascribes a great deal of importance to the moon. It is believed to exert a powerful influence over the earth and all that inhabit it, its effects being particularly potent when it is at its fullest. This is when witches are thought to convene, and is often considered a propitious time for conducting pagan rituals. Robert’s selection of a full-moon night therefore highlights the diabolical nature of his fratricide.