In the depths of winter, Shen Yan, a poor scholar, meets a speaking gray rat inside his rice jar. The gray rat has come to borrow grain for its injured mother, so he helps it with a pinch of white rice and writes an IOU bearing 'no interest charged'. Later, the gray rat secures a grain-shop job for Shen Yan, and together they inadvertently uncover the master’s plot to sell relief grain privately and forge account books. Faced with the temptation of fifty taels of silver and framed accusations, Shen Yan insists on keeping honest records. With help from neighbors, porters, and the gray rat, the truth is brought to light. After the autumn harvest, the gray rat returns the rice as promised. Both human and rat uphold their integrity and form a warm, lasting bond of friendship.