Zhang Yi'ang, a police officer who has been away from frontline criminal investigation for years, is dispatched to Sanjiangkou after receiving an anonymous tip from the provincial department. Shortly after arrival, he witnesses the murder of his criminal investigation captain. While clearing himself of suspicion, he unexpectedly arrests a serial killer, quickly gaining prestige. As he focuses his investigation on the gang of Zhou Rong, a wealthy local businessman, the numerous bumbling thieves and their infighting create a butterfly effect that ironically help him and his team. Supposed fate brings him together with all the thieves, and he ultimately prevails, uncovering the motive behind his colleague's murder and bringing the real culprit to justice.