Based on Tove Jansson’s beloved novel, The Summer Book tells the story of Sophia, a nine-year-old girl who is growing up fast, and her grandmother, who is nearing the end of her life. Together with Sophia’s father, they spend time at their family’s summer home on a tiny unspoiled island in the Gulf of Finland, exploring the islet, talking about life, nature and everything but their feelings about Sophia's mother's death and their love for one another. By the end of the summer, emotional wounds are healed, bonds are deepened, and the grandmother is able to leave this life peacefully.