Ngao Jai tells the story of two male twins, Watit and Rut, who were separated from each other, leading completely different lives. One twin belongs to the high society in the big city while the other one leads a modest but good life in the countryside. When Watit, the twin from the big city gets hurt by someone, the father asks Rut, the other twin to take the life of his severely ill twin, leading a life under his name by pretending to be his unknown brother in hope to find the person who tried to kill his brother. The main heroine, Maytinee, is the bride-to-be of Watit. But their engagement is only based of a business deal and not of affection. When his brother replaces him, she doesn't notice the substitution at first and marries him anyway. But she gradually begins to realize that he is a different man, falling slow in love with his different attitude.