A new investigation was entrusted to Mao Mao... by the empress customs officer, this time! Indeed, the noble lady wonders if, at the time, she would not have cast a spell on her husband, who had died after losing her mind. The apothecary then discovers the heavy secret of the imperial family... Shortly afterwards, she is invited to a strange evening where young girls tell frightening stories in a room with a sinister atmosphere... So what is the riddle that Mao Mao is supposed to solve?