Donald "Don" Eppes is a fictional character and one of the protagonists of the CBS crime drama Numb3rs. He is portrayed by Rob Morrow.Don is an FBI Special Agent who runs the FBI Violent Crimes Squad in Los Angeles. Don recruits his mathematical genius brother, Charlie Eppes, to help him and the Bureau solve some of their most difficult cases. Don makes great sacrifices in his personal life in order to devote himself to his career, which to him is more of a way of life than a mere job.