"Luzhou Iron Lock" - At the end of the Southern Song Dynasty, the Mongolian army pressed on the border. In order to prevent the enemy from advancing southward, Shen Jiang, the defender of Luzhou, ordered the casting of a giant iron lock to lock the Yangtze River across the Yangtze River. However, he gradually discovered that the formula of the iron locks in the city had been secretly tampered with, and excessive amounts of phosphorus and sulfur were added - an alloy that would become brittle and disintegrate in the face of war. The mole is around, and the army will arrive in three days. Shen Jiang must find out the person who wants Luzhou to die without a fight before the iron chain breaks.
