Four teenage girls meet with one of their fathers at a restaurant, where Helana—a time traveler from 500 million years in the future—reveals that a mid-century global conflict will nearly wipe out 95% of life on Earth, but her three friends will become key figures in humanity's resistance and eventual rebuilding. Later that night, as the girls have a sleepover, Helana confides her fears about forgetting her origins and not knowing her role in the changed timeline, while Ella encourages her to focus on living day by day rather than worrying about predetermined futures.