On the eve of her 25th birthday, Catherine, a troubled young woman, has spent years caring for her brilliant but unstable father, a famous mathematician. Now, following his death, she must deal with her own emotions; the arrival of her sister and the attentions of Hal, a student of her father’s who hopes to find valuable work in the notebooks that her father left behind. Over a long weekend, a burgeoning romance and the discovery of a mysterious notebook draw Catherine into the most difficult problem of all: How much of her father’s madness—or genius—will she inherit?