Marfa Girl follows Adam, a directionless 16-year-old boy, in the days surrounding his sixteenth birthday. The film details his relationships and interactions with the other inhabitants of the small Texas town, including his 16-year-old girlfriend Inez, his 23-year-old neighbour Donna who attempts to seduce him as a sixteenth birthday present, his teacher, who is eager to deal out corporal punishment, and a newly arrived local artist, who also seeks to have sex with Adam.