More than 2,000 years ago, the Zhao State decided to attack the Liang State sandwiched between the two states in order to conquer the equally powerful Yan State. As a result, Liang City, which had only 4,000 women, children and civilians, was surrounded by the Zhao army of 100,000. In times of crisis, the King of Liang (Wang Zhiwen) asked the Mohist school, which was famous for defending the city, for a garrison that could resist the Zhao army, but he was met by the unprepossessing Mohist Ge Li (Andy Lau) who advocated "universal love and non-aggression" and fought alone. Ge Li won the battle by surprise, and the Zhao army returned empty-handed. Later, in order to cope with the huge attack of the Zhao army at any time, he personally trained and manufactured countless special weapons. Everyone in Liang City was impressed by him, and he was also loved by General Yi Yue (Fan Bingbing). However, murderous aura also descended on him at this time.