The futuristic ocean city of Shencheng relies on the Ten Thousand Lantern Array to sustain its prosperity, yet it conceals memories of a disaster that has been erased. Yuan Xi, an unofficial lantern collector, hears the voice of her younger sister, Lu Wei, who disappeared seven years ago, during an incident in which the Ten Thousand Lantern Array goes out of control. Together with Qi Ling, a genius engineer, and Ya Qing, a survivor of Nanwan, she investigates the truth. They gradually discover that the city's radiance is built upon forgetting. Faced with a choice between order and truth, between individuals and the city, the three decide to let the Ten Thousand Lanterns stop concealing memories and truly illuminate those who have been forgotten.