David Sears grew up in the shadow of his brilliant sister, Diana, convinced by their father that she would accomplish great things. Instead, she married and had a son, Jason, who like David and Diana s father is schizophrenic. Her husband, Mark, a geneticist, never made peace with Jason s condition. Perhaps this is why Diana will not accept the authorities conclusion that Jason s drowning death was accidental. Or perhaps Diana is going mad. As she builds a case against her husband and the seductive qualities of her manic energy become impossible to ignore, David finds himself afraid for his own family s safety. In The Cloud of Unknowing, Cook explores the power of blood and family mythology.