Cow-herding boy A Niu chances upon the celestial maiden Wan Yue bathing, and out of selfish desire steals her immortal wings, causing Wan Yue to be stranded in the mortal realm. The two live together, marry, and have a child, but ten years later Wan Yue discovers the truth and, heartbroken, returns to the heavenly palace. A Niu takes their son An Er and ventures up to heaven to seek his mother. The Jade Emperor investigates the cause and effect, sentencing A Niu to herd oxen at the Heaven River for thirty years to atone for his sin, without forcing Wan Yue to forgive him. After going through many trials, the family is able to stay together at the Heaven River, and the world calls A Niu the Cowherd.