Numb3rs Episode 3.12 Nine Wives

When a teenage girl is found beaten but alive on a desert road, the FBI discovers she escaped from the fundamentalist leader of a polygamous cult, who is on the FBI's most wanted list for using polygamy as an excuse to marry and rape young women. After finding a coded map at the leader's last known location, Charlie mathematically determines it's a family tree, and the leader's genes aren't good for offspring unless he kidnaps one of the last remaining non-inbred females in his cult to procreate with and start a new sect in another country.