These days, few people know that Conan Doyle, the famous author of detective stories about Sherlock Holmes, was also a famous public figure, a defender of the unjustly convicted. Conan Doyle's intervention helped commute the sentence of his friend accused of high treason, restore legality in the high-profile case of an Indian-born Englishman who was the victim of xenophobia, and finally free Oscar Slater, convicted of murdering a wealthy lady. Sentenced to death, which was then commuted Lifelong hard labor, Slater spent more than 18 years in prison, forgotten by almost everyone. Almost everyone, but not Arthur Conan Doyle. The writer managed to free Slater by conducting his own investigation, and his main weapons were observation and clear logic - exactly what brought worldwide fame to the hero of his stories. The book also tells about a person sentenced to execution, whose innocence was proven without modern forensic methods, and about a unique investigative method described in the stories of Sherlock Holmes and then applied to a real crime.