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, wholike David and Dianas fatheris schizophrenic. Her husband, Mark, a geneticist, never made peace with Jasons condition. Perhaps this is why Diana will not accept the authorities conclusion that Jasons 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 familys safety. In The Cloud of Unknowing, Cook explores the power of blood and family mythology.