The plot and main characters of West Side Story are loosely based on Shakespeare's Romeo and Juliet. The story has been modernized and Americanized with the introduction of a racial theme - Tony, a member of an established white gang (the Jets) falls in love with Maria, whose brother is a member of the rival Puerto Rican gang (the Sharks). The Jets are contemptuous of the Sharks and look down on them as foreign newcomers. The Sharks wish to establish themselves as Americans and defend their new territory. As in Romeo and Juliet, the rivalry escalates and leads to great tragedy.