That mysterious third Olsen sister is set to become a little less mysterious.

Elizabeth Olsen, who garnered rave reviews at the Sundance Film Festival for her performance in the indie 'Martha Marcy May Marlene,' will star opposite Dakota Fanning in 'Very Good Girls,' Deadline reports.

The film follows two teenage girls through a summer in New York City. After they graduate high school, each becomes determined to lose her virginity, and things get complicated when they fall for the same charismatic street artist.

The cast also includes Peter Sarsgaard, Dustin Hoffman and Sissy Spacek.

Best guess says Sarsgaard plays the charming street artist ala his young-lady-seducing character in 2009's 'An Education.'

[via Deadline]