This article aims to analyze the ongm of the ``cavalry`` fantasy of Gail Hightower, who is one of the protagonists in Light in August. Until now, studies on him have been focused on the question whether he is saved from his fantasy at the last moment or not. A majority of critics argue Hightower comes to get salvation through helping with Lena``s delivery, returning to and reconciling with the community at last. Others disagree with such a positive interpretation, and assert that he fails to be saved from his suffering in that he dies in his lifelong fantasy, which distorted and destroyed his life. However, there have not been enough studies on the origin of his fantasy. With the help of Freud and Lacan, this paper tries to prove that Hightower``s fantasy comes from a self-defense mechanism, not from a genuine worship of his grandfather``s heroic death. In short, Hightower developed the obsessive passion for his grandfather``s heroic military exploits to conceal his inappropriate hate toward his father, providing a typical example of Oedipus complex. Young Hightower retained a strong sense of unity with his mother, who had been, he believed, suffering to death from her husband``s self-righteous negligence. As a result, young Hightower transferred his desire of patricide to a more positive feeling of hero worship of his grandfather. In conclusion, it can be said that Hightower``s fantasy comes from his anxiety hysteria that he might commit a patricide, which caused him to create a hero worship to conceal and divert the horrible desire.