A year-long investigation reported on Friday’s “20/20″ was the number one show at 10pm, topping newsmagazine competition NBC’s “Dateline” by more than a  million viewers. ABC’s Amy Robach revealed the home of the Fundamentalist Latter Day Saints, the largest polygamous community in America, is still ruled by their leader and prophet Warren Jeffs, even though he is serving a life sentence in prison.

“20/20″ drew 5.8 million viewers and led the hour in A18-49 and A25-54 viewers. “20/20″ was up over its year-ago performance in Total Viewers (+16%), A18-49 (+25%) and A25-54 (+24%).