To many contemporary critics sensation fiction by Braddon and Wilkie Collins was feeding a dangerous and unhealthy craving for violent crime and the depiction of immoral and unwholesome characters. Sensation fiction's preoccupation with secrets, and the revelation of those secrets and crimes, are often so intrinsic to the plot that they must be considered as the antecedents of the emergent detective novel. Today Braddon is frequently credited as one of the most important writers of Victorian crime fiction, and amateur and professional detectives frequently appear in her work.

Published in 1886, Cut By the County shows the progression from sensation fiction to detective fiction. The novel contains an amateur detective, in the form of Colonel Weldon Stukely, pitted against a professional detective, Mr. Penwern of Scotland Yard.

Colonel Stukely returns to England after many years, and visits his old friend Sir Allan Darnel. Sir Alan's second wife, Clare, is a widow of mysterious origins, and because of this she has been ostracised by local society. Sir Allan's daughter, Grace, confides in the Colonel that she is secretly engaged to a poor French painter, who the Colonel fears will blackmail her into keeping the promise she made as a schoolgirl.
Soon the Colonel is forced to become an amateur detective to protect Grace's reputation when Sir Allan is shot, a large sum of money stolen, and Clare is under suspicion. The secrets of Clare's past have returned to haunt the present.

Today Braddon is best remembered for Lady Audley's Secret (1862), with its amateur detective Robert Audley. As the sensation novel developed into the detective novel of the 1880s and 1890s, Braddon was determined to maintain her position within this modern genre. In 1899 she published His Darling Sin which features Braddon's most prominent professional detective, John Faunce. Critics and biographers have noted that the detective fiction loving policeman bears a marked resemblance to Wilkie Collin's Cuff from The Moonstone (1868), and Robert Lee Wolff described Braddon's novel as 'a sophisticated story of hard boiled society people.'

Faunce is hired to prove the innocence of Lady Perivale, a rich young widow, whose reputation has been ruined by Colonel Rannock, whom she has refused in marriage. He claims she travelled to Algiers with him and lived with him as his mistress. As a consequence of the rumours, and witnesses who saw the woman in Algiers say she looked just like her, Lady Perivale has been cast out of society, and even the man she loves, a novelist called Arthur Haldene, believes the worst of her. In the meantime Rannock has gone missing, and may have been murdered. In the course of his investigation Faunce discovers the identity of the mysterious woman who was living with Rannock, and plots an elaborate scheme to clear Lady Perivale's reputation.