In the 1930s, Su Wenli, a Shanghai socialite who had studied in Europe for many years, returned to Shanghai from Paris. The next day, she was invited to Ma Minlan's house for lunch. Ma Minlan's husband Hu Yunlang fell and died in the bathroom at home that morning. Inspector Luo Qiuheng of the police station judged that Hu Yunlang died of arsenic poisoning, so he took the maid Xiao Taozi away for investigation. Although she was cleared of suspicion, Xiao Taozi was still fired by the Hu family. Seeing that she was smart, Su Wenli took Xiao Taozi in. Xiao Taozi became her maid, best friend and detective assistant. Inspector Luo was deeply impressed by Su Wenli's intelligence and insight in analyzing the case, so the two formed a golden partnership and jointly solved a series of bizarre cases.