Abby and her family were semi-normal people who had their own problems in life and each dealt with it in there own ways. In this, their own personalities created the plot and central story of the book. The mother, a rigid Catholic housewife and a working mother, was always good to her family. Her father was a strict discipline man with his views of male and female roles. He was a rough and harsh father, according to him the girl's place is in the home and the boy must live up to a rigid of "masculinity". The sister who is Abby is the daughter. Abby lives a seemingly normal childhood in a rural Catholic community. She lived in a world that had offered her faith. In her childhood, she has always been living under her father order. Abby is determined to retrace her lost sibling's dark descent embarking upon an emotional journey that will exanimate the strength of her spirit, and deny everything she once believed about her family and herself. Sam is Abby's lovable younger brother whom she protected and adored. He and Abby were nearly inseparable: sharing the secretive, messy world of childhood. At a teenage age he wasn't safe having from his father's bullying, send into a world of violence and hatred and disappears from home.
Each of their personalities triggers the central plot of the story. Sister is a sad, fascinating tale of the past and present of family and love. It tells a story of a young woman about to start her own family. She searches out the truth about the damaged family she grew up in. Of particular interest to her is the fate of her younger brother, who ran away as a teenager and never came back. Abby moves us back and forth in time with her story to show us the interior of her family: her devoutly Catholic mother, rough and harsh father, and misfit brother Sam. Her memories of her younger brother Sam, who disappears at teenage age, and her changing understanding of her parents allow her to differentiate between the versions of the past she is presented with.