Together they devised an operation to save "Blue Babies"—infants born with a heart defect that sends blood past their lungs—and Cooley was there, as an intern, for the first one. He remembers the tension in the operating room that November morning in 1944 as Dr. Blalock rebuilt a little girl's tiny, twisted heart. He remembers how that baby went from blue to pink the minute Dr. Blalock removed the clamps and her arteries began to function. And he remembers where Thomas stood—on a little step stool, looking over Dr. Blalock's right shoulder, answering questions and coaching every move.