The Louisville native and graduate of Notre Dame arrived in Los Angeles in the late 1980s and served as a production assistant on films that spotlighted his movie star cousin (e.g., "Cocktail" and "Rain Man" both 1988). Beginning with 1989's "Born on the Fourth of July", Mapother moved in front of the cameras, but he spent almost a decade away from the silver screen, mostly working as a substitute teacher or penning screenplays. By the late 90s, though, Mapother was once again pursuing an acting career, landing small roles in films like "Without Limits" (1998), "Magnolia" (1999) and "Mission: Impossible II" (2000). His intense portrayal of an abusive husband and father in "In the Bedroom" certainly raised his profile and boded for a promising career. Along with appearances in a few more of his cousin's films, "Vanilla Sky" (2001) and "Minority Report" (2002), Mapother racked up supporting credits in "Swordfish" (2001), "Self Storage" (2002), "The Kiss" (2003) and "Suspect Zero" (2004), and made an indelible appearance in the horror hit "The Grudge" (2004) as one of the American relatives who falls prey to the violent cure on a Japanese home.
Mapother also scored in guest shots on popular series such as "CSI: Crime Scene Investigation," "CSI: Miami," "Law & Order Special Victims Unit" and "Touched by an Angel." In 2004 he appeared in a recurring role as the mysterious antagonist Ethan who menaces the crash survivors during the first season of the hit ABC drama "Lost" (2004- ).