A Ma Soeur! is a provocative and shocking drama about sibling rivalry, family discord and relationships. Elena is 15, beautiful and flirtatious. Her less confident sister, Anais, is 12, and constantly eats. On holiday, Elena meets a young Italian student who is determined to seduce her. Anais is forced to watch in silence, conspiring with the lovers, but harbouring jealousy and similar desires. Their actions, however, have unforeseen tragic consequences for the whole family.