At a train station floating in the cloud, a mysterious red tail catches the boy’s attention. Chasing the red tail, the boy travels through countless magical places, runs into bizarre creatures, and finally he meets the gentleman, who seems to know his secrets more than he does. When the red tail reminds the boy of his own memory and sadness, what are the secrets hidden behind, and where will they lead him next? Inspired by Wang’s same named comic story, the mysterious red tail leads viewers on a magical journey, creating a poetic metaphor of people’s childhood memories.