A different summer. Antoine, a teenager, is on holiday at the seaside with his parents and his younger brother, Titi. Both spend most of their time drawing, at restaurants and on the beach. But one day Hélène and her mother come to spend a few days with the family and her presence will change Antoine's life. In 'A sister', Bastien Vivès, a master storyteller, conveys the stumbling awakenings of adolescent feelings.