In 1944 a groundbreaking operation repaired the congenital heart defect known as blue baby syndrome. The operations success brought the surgeon Alfred Blalock international fame and paved the way for open-heart surgery. But the technique had been painstakingly developed by Vivien Thomas, Blalocks African American lab assistant, who stood behind Blalock in the operating room to give him step-by-step instructions.The stories of this medical and social breakthrough and the lives of Thomas, Blalock, and their colleague Dr. Helen Taussig are intertwined in this compelling nonfiction narrative.