Celie writes that Pa has taken her other child, the boy, from her. But Celie does not believe he has taken this child out to the woods to kill it. Instead, Celie thinks Pa has sold the child to a man and woman in the nearby town of Monticello. Celie worries that her father will soon have sexual designs on her younger sister, Nettie. Celie vows to protect her sister from harm, "with God's help."
It seems that Pa does not have designs specifically on Celie—Celie comments that she herself is not especially pretty, and her skin is dark. Rather, Pa seems to want simply to abuse his own daughters. Celie recognizes this impulse in Pa, and does her absolute best to make sure that Nettie escapes his sexual abuse.