On the eve of her twenty-seventh birthday, Catherine, a young woman who has spent years caring for her brilliant but unstable father, a mathematical genius named Robert, must deal not only with the arrival of her estranged sister, Claire, but also with the attentions of Hal, a former student of her father's who hopes to find valuable work in the 103 notebooks of Robert's. As Catherine confronts Hal's affections and Claire's overbearing plans for her life, she struggles to solve the most perplexing problem of all: How much of her father's madness--or genius--will she inherit?