Lumen Pierce appears on the fifth episode.
Lumen Ann Pierce is a fictional character portrayed by Julia Stiles in the Showtime television series Dexter , season 5 . She remains for the rest of the season , and leaves following the season 5 finale , `` The Big One '' . In season 5 , episode 5 , `` First Blood '' , Lumen is revealed to have been beaten and gang raped by a group of men , including Boyd Fowler .