In the history of the world, revenge was allowed for a long time before modern legal system. It was justified as a means of realizing justice. Ancient law also allowed public revenge based upon the principle of retributive justice. But revenge was illegalized by modern law with the advent of modern era. With the illegimitization of public revenge, a new genre of detective novel also makes private revenge illegal in its narrative. A revenger’s voice was not allowed, and it was considered as violent, barbarous in a detective novel. In A Study in Scarlet and The Sign of Four, a revenger’s voice is blocked by the detective’s one. In A Study in Scarlet, revenger’s voice is heard through the chasm between poetic justice and legal justice. Even though the revenger’s voice attracts many readers and gains their sympathies, a detective intervenes and ultimately blocks the revenger’s voice. In The Sign of Four, a revenger is portrayed as a disgusting and repulsive criminal. and his motives for murder have no empathic appeal to the readers. At the end of these two novels, a detective captures a revenger and makes him go to prison. In Conan Doyle’s detective novels, a detective becomes a new hero who realize both poetic and judicial justice while a revenger becomes a criminal who violates the law and order of society.