The proud father relayed the news over a candlestick-style telephone to family and friends in Agawam, Massachusetts, and beyond. "It's twins! God Bless! Lil has given birth to identical twin girls!" Before long, tiny Julia and Agnes Tatro were taking their first tottering steps and trailing each other into mischief. They were the spitting image of each other, from their wispy flaxen locks to their knobby knees -- except for the deep dimple that Julia wore on her left cheek and Agnes wore on her right. It was the 1920s, the days of new- spinning Victrolas and sporty Model Ts; of old-fangled doctors whose black bags contained, first and foremost, a stethoscope and vials of morphine. Medicine's reach was skin-deep; the source of most ills too complex to grasp. People knew about genes -- in the case of identical twins, their identical set -- but they were as distant as magma at the earth's core, and no one knew what they were made of or the good or bad extent of an individual's inherited array. And so, even as Julia and Agnes Tatro blossomed into pretty, spunky girls who reached out to life, no one suspected what lurked beneath the surface. And it gave no sign of itself. It inched along its harmful course in too quiet a way, just as, in all likelihood, it had been doing even before their mother knew she was pregnant.