Benson Hagglethorn was a human male. He is mentioned in Grave Peril.
Benson was an abusive drunk, and his wife feared him. One day Agatha inadvertently suffocated their child while trying to muffle her cries in an attempt to avoid Benson's wrath falling upon the baby. Her guilt and rage over the child's death, and herself causing it, led her to take up an axe and kill her husband.