In the spring of 1986, the Chernobyl nuclear power plant explodes in the Soviet Union and a girl named Mimi arrives in a small village in the Tavastia region of the Southern Finland, filling 15-year-old Mariia's life with light for a moment. After twenty years, facing a dead end in her own life, a grown-up Mariia visits her childhood home and recalls the summer of her youth and the tragic autumn that followed. In a flood of memories, Mariia is forced to confront her past. Returning to the summer of her first love in the 80's, Mariia must let go of the guilt that swallows up all the light and forgive other people as well as herself.