Teacher An has spent nearly thirty years teaching the children of fishing families on Hongze Lake, carrying education from boat to boat while sacrificing his own life ashore. After a professional evaluation shakes his faith in the value of his work, he is forced to confront the cost of his devotion: his late wife, his children, and the possibility of a new family with Yueying, a woman who seems willing to share his hardships. As local officials and former students try to arrange a successor and a better school boat, An struggles between personal happiness and the weight of responsibility to his students.