Along with his young son, Ji-ho, Woo-jin misses his wife Soo-a, who died after promising to return a year later with the rainy season. Miraculously, they reunite with Soo-a when the rainy season comes around, but she has no memory of her husband and son whom she dearly loved.
While desperately searching for his missing daughter, Hae-kwan comes across an AI satellite robot that remembers sounds from all over the world. Rejuvenated by the robot's abilities, Hae-kwan begins to track down his daughter's voice. As they continue their journey, they form an unforgettable bond.
