Martin Odum is an FBI agent. Odum is a specialist who can transform himself into anyone he needs to be. His alternate identities, called “legends,” are so complex and thoroughly established that they almost take on lives of their own. He has a wife named Sonya Odum, but he also has a history with his assistant, Crystal Maguire.
At the end of the season two finale, it was revealed that Martin's real name is Alexei Volkov.