In northwest China, 48 BC (100 BC on screen in the English version), a security company under Han China’s current government called The Silk Road Protection Squad is committed to stopping battles and promoting the idea of peace. Huo An (Jackie Chan), the captain, successfully averts a battle. The group returns to their unnamed home city, where Huo An’s gentle Uyghur wife Xiuqing (Mika Wang) serves as a schoolteacher for orphans. However, the government uncovers evidence that someone in the group is corrupt, causing the entire group to be sentenced to construction work at Wild Geese Gate, a ruined fortress. Once they arrive, the group pays respects at the shrine of a fallen Chinese general. They originally were child-slaves of Han descent and this general had later rescued them.
Not long after, Wild Geese Gate is threatened by a legion from the Roman Empire in need of water and supplies, among which is a blind boy named Publius (Jozef Waite). After a stale-mated duel between Huo An and Lucius (Cusack), the Roman general, the latter agrees not to assault the city in return for being let inside. The legion uses its superior engineering skills to speed up the construction work, an act which boosts the morale and happiness of the inhabitants, who are divided among several different ethnic groups, such as Chinese, Uyghur, and Turkic. Huo An returns the favor by sending men to assist Lucius’s envoys in reaching the Parthian Empire. A celebration is later held and Huo An is made an honorary centurion.