The narrative opens with a seasoned medical practitioner's inexperienced locum being summoned late at night to a mysterious house near Regent's Park to attend a terrified young woman. She is discovered with suspicious marks upon her neck, while a broken door and a concealed packet of cocaine hint at a sinister environment. The woman's husband, Nicholas Frood, is revealed to be a degenerate and unstable drug addict prone to violent jealousy, creating an atmosphere of constant menace. The narrator departs, profoundly unsettled, but the incident remains etched in his memory until a chance discovery reveals the empty house.
Later, the young doctor relocates to Rochester to take over a small medical practice, only to find himself once again entangled in the same troubled life. He discovers that Mrs. Frood has fled thither to escape her husband's persecution, living in seclusion under the protection of her relatives.
The husband soon arrives in pursuit, leading to a series of tense encounters and atmospheric wanderings through the old streets and along the riverbanks of the historic town. When Mrs. Frood abruptly vanishes without a trace, the local police sergeant launches an investigation that gradually uncovers disturbing clues washed ashore by the tidal river. As personal concern deepens into a quest for justice, the narrator enlists the aid of a legal-medical expert to sift the emerging evidence. The narrative builds toward a resolution of the dark puzzle, contrasting the quiet beauty of the ancient Kentish architecture with the grim reality of a human tragedy.
