"The Silent Sister" is a novel by Diane Chamberlain that explores themes of family secrets and personal identity. The story follows Riley MacPherson, who discovers hidden truths about her deceased brother and the life of her estranged sister, Lisa. As Riley delves into her family's past, she uncovers a web of lies that challenges her understanding of her loved ones. The narrative unfolds through Riley's perspective, revealing the complexities of relationships and the impact of silence on their lives.