Mapother has become widely known as a character actor, who sometimes plays scary or otherwise dark characters. He played a pivotal role in Todd Field's In the Bedroom, and is perhaps best known as Ethan Rom in the TV show Lost. The character was killed off early in the first season, but appeared in seven later episodes mainly through flashbacks, once due to time travel and another in an alternate timeline. In all, he appeared in eleven episodes of Lost.
Mapother has also had considerable roles in a series of independent films, such as The Lather Effect, Moola, Hurt, and Another Earth. Mapother starred in The Burrowers as a former Indian fighter who joins a posse to help find missing white settlers, only to discover that the hunters have become the hunted. Wikipedia