After office worker Su Xiao feeds a stray black cat, Heiya, she unexpectedly gains the ability to understand animal language. One night, she digs up money following Heiya's guidance, but unearths dismembered remains instead, getting herself tangled in a serial murder case. Heiya controls the urban animal intelligence network, and Su Xiao uses animal eyewitness clues to assist female police officer Liu Dan and Chief Zhang Lei in solving cases. Twins Chen Qianfan and Chen Xingzhou split up to commit crimes: the older brother wears a silicone mask to disguise himself as a woman to lure and murder single girls, turning the victims into sculptures hidden in a secret room, while the younger brother is responsible for creating alibis. Relying on small animals to obtain key evidence, Su Xiao helps the police capture the real culprit. After this case, Su Xiao becomes an unofficial auxiliary investigator for the security bureau, using animal intelligence to guard the safety of ordinary people.