The story opens in the bleak, rainy town of Slopperton, where a model young man named Jabez North is universally admired for his piety and benevolence, despite unsettling hints from a phrenologist concerning his complete lack of conscience. As a foundling raised by the workhouse, Jabez masks a cold, calculating ambition beneath a meek exterior. Meanwhile, a wealthy East Indian named Montague Harding returns home and seeks out his widowed sister, Mrs. Marwood, at her lonely residence called the Black Mill.
That same stormy night, Mrs. Marwood's long-lost, dissipated son Richard—known as Daredevil Dick—returns home in desperate repentance. Touched by his contrition, Mr.
Harding provides Richard with a generous sum of money and a letter of introduction to start anew at a merchant's office in Gardenford. Unbeknownst to them, Jabez North executes a meticulous and sinister midnight escape from his academy, committing a horrific crime that leaves a helpless sick boy dead to ensure his silence. The following morning, Mr. Harding is found brutally murdered in his bed, and his valuable pocket-book is missing.
Richard is swiftly hunted down by detectives and arrested, his case severely compromised when he foolishly burns his uncle's letter of introduction and bears dark stains upon his coat. During the subsequent trial, Richard's defense rests on the plea of temporary insanity brought on by brain-fever and despair, ultimately resulting in a verdict of not guilty by reason of insanity, sparing him from the gallows but condemning him to a lunatic asylum. Years later, Jabez North continues his ruthless pursuit of wealth and status, eventually rising to elegance in Paris. There, he orchestrates a sophisticated and merciless plot of revenge and betrayal against a proud Spanish heiress named Valerie de Cevennes, who has secretly married the handsome opera-singer Gaston de Lancy. Through cruel manipulation and a series of devastating exposures, Jabez drives Valerie to a desperate act of retribution that culminates in a tragic and fatal finale at the opera.
