Sikong Zhen stumbles upon a hidden cache of mechanical beasts slumbering beneath Chang'an's streets and becomes obsessed with understanding their origins. When Wu Zetian catches wind of the discovery, she dispatches her trusted aide Shangguan Waner to probe deeper into what's really happening underground. Meanwhile, the shadowy Yaotian organization pursues their own agenda, viewing these machines as leverage for power. What begins as isolated secrets quickly spirals into a three-way collision of interests as each faction races to control or contain the threat. The tension builds until the mechanical beasts awaken, forcing every player in Chang'an's political game to set aside their schemes. Ancient enemies and reluctant allies must choose between their ambitions and the city's survival. The series balances comedic moments with genuine stakes as characters navigate betrayal, desperation, and the possibility of unexpected cooperation. What emerges is equal parts spy thriller and action adventure, where loyalty gets tested and the cost of peace demands sacrifice from everyone involved.