Old Zhang and his wife live a quiet, ordinary life. While venturing into the mountains, they risk their lives fighting a giant python to save an unfamiliar child, Yang Jian, and suffer severe injuries. The little dog beside the child transforms into Xiaotian Dog and drives the python away. The Jade Emperor reveals in a dream that Yang Jian is his nephew, whose divine powers and memories have been sealed, and entrusts the couple with raising him. Given the name Erlang, Yang Jian gradually adapts to mortal life, but when his seal is torn open, his uncontrolled divine powers attract the greedy Dapeng, a military strategist who covets his power. Dapeng kidnaps Erlang, prompting Old Zhang, his wife, and Xiaotian Dog to pursue them. In the end, Erlang awakens his divine powers and defeats Dapeng. When his period of mortal training ends, he bids farewell to his adoptive parents and returns to Heaven, leaving behind a moving bond between immortals and mortals.