The story of the surgery that made Ben Carson famous -- and its complicated aftermath

For months, a team of physicians and nurses had rehearsed for the delicate surgery. For hours they had prepped the two tiny bodies perilously joined at the head. And when it came time on that day in 1987 to put a knife to the large vein connecting them -- the most fraught step in the groundbreaking operation to separate infant conjoined twins -- Benjamin Solomon Carson, the brilliant young pediatric neurosurgeon who had overseen the babies' case from the start, offered his scalpel to his boss.