Xiaoman and his younger sister Xiaojia picked up a curtain puppet named "Little Bell" on the road. The younger sister Xiaojia considered that Little Bell might still have performance tasks, and suggested returning it to the puppet troupe immediately.
The Public Security Bureau intercept a telegram notifying foreign agents to retrieve the "110 secret". Shi Yan, head of the Reconnaissance Section, starts a campaign of counter-espionage, but one of his agents is soon killed on board a train.