I just finished the book "The Murder on the Links" by Agatha Christie. In the end it is revealed that
was the murderer. But there is no explanation on how she did it. Poirot deduces that she overheard the Renauld's plan and killed him in the night. But since the beginning Poirot claimed that a woman can not dig a grave. Then how did she dig it? And if Renauld had already dug the grave, then how did she cover the body in soil?