During the early colonial days, Hong Kong's first ethnic Chinese Baroness, Lady JUDY FLETCHER (Adia Chan), by mishap, lands in the slums of Yau Ma Tei, as a result of her foreign husband's downfall and disappearance. While there, a prostitute is murdered, and the incident has many similarities to the attacks ascribed to the serial killer in Britain, Jack the Ripper. JUDY is accused of murder by security guard DIK TAK-YING (Tsui Wing), ending up in jail. Fortunately, her former butler KWAN YAT-FU (Ben Wong) sets aside grudges against her and helps clear her name. Meanwhile, JUDY re-encounters her estranged younger sister PAU MUI-TAI (Alice Chan) and adopts an orphan named TING HIU-YIU (Kaman Kong), living a simple life along with her neighbors such as NGAI SO-KAR (Jeannie Chan) and YAU CHI (Dickson Yu). The killer resurfaces. To protect everyone, JUDY demonstrates her Sherlock Holmes-like abilities to probe into the matter, only to realize it's not that simple. Both her disappeared husband and YAT-FU are suspicious. The killer announces a killing spree as provocation, aiming at MUI-TAI and HIU-YIU. Facing its darkest hour, the whole city is plunged into a heightened vigilance.