Arthur Conan Doyle's 1890 work of detective fiction, The Sign of the Four, is the second full-length novel featuring the genius detective Sherlock Holmes and his loyal companion, Dr. John Watson. Overtly, the novel is an entertaining romp through layers of mystery and intrigue; however, it is backgrounded by Conan Doyle’s satirization of British police and their ability (or, as he claimed, lack thereof) to solve crimes.

During the Victorian period, the British police force faced heavy criticism for its apparent inability to tackle rising crime and solve preexisting cases. Founded in 1829, the Metropolitan police force was established in response to the modernizing needs of major British cities. Officers were recruited from the lower class to deter claims of inequality or class-based discrimination. It was not until the 1870s, nearly fifty years after the force’s original conception, that a proper detective department was established. In 1888, just a few years after the founding of this detective department, Jack the Ripper began to terrorize Londoners. The London Criminal Investigation Department (CID) sought to bring him to justice to no avail. Conan Doyle’s 1890 novel, written just two years after the Ripper’s spree, pointedly addressed the shortcomings of the British police and offered a satirical solution: a consulting detective of singular intellect and off-putting temperament, who could solve any case placed before him. Indeed, Holmes is something of a foil to London’s short-sighted, seemingly incompetent police force. 

When Mary Molston requests his aid, she explains that the police failed to find her father and determine the cause of his disappearance. Moreover, Thaddeus Sholto demonstrates a marked aversion to the police from his first note to Mary, instructing her not to bring the police. He later states, "there is nothing more unaesthetic than a policeman. I have a natural shrinking from all forms of rough materialism." Not only are the London police incompetent but, according to Sholto, they are unrefined and lack Holmes’s suave demeanor. While Sholto’s distaste for police officers appears to be rooted in a classist mindset, it was not unusual for contemporary Londoners to fear and avoid the force dedicated to their protection; indeed, police were commonly regarded as brutist, provincial, and unnecessarily violent. Because Holmes's character stands apart from this formal and disreputable institution, he earns an audience with Sholto and gains access to the case.

But Holmes is more than a palatable alternative; in fact, his methodology is novel and technologically innovative. When he measures Tonga’s footprint, Holmes uses a nascent form of fingerprinting that significantly predates the development of actual fingerprinting. His deductions are impressive but empirically based, as seen when he determines that one of the culprits in Bartholomew Sholto had a peg leg from a stump-like impression left at the crime scene. Holmes, too, discerns that the killers escaped by means of the Thames, while the police, naturally, if inaccurately, mistake Thaddeus Sholto for the culprit.

In this way, The Sign of the Four, in addition to being a fantastic and thrilling piece of detective fiction, doubles as an indirect satire of the police force in Conan Doyle's contemporary London.