The Sign of Four was the second novel featuring which famous fictional detective, following A Study In Scarlet?
Arthur Conan Doyle Sir Arthur Ignatius Conan Doyle KStJ, DL (22 May 1859 – 7 July 1930) was a British writer best known for his detective fiction featuring the character Sherlock Holmes. Originally a physician, in 1887 he published "A Study in Scarlet", the first of four novels about Holmes and Dr. Watson. In addition, Doyle wrote over fifty short stories featuring the famous detective.
Colin Dexter Norman Colin Dexter, OBE (29 September 1930 – 21 March 2017) was an English crime writer known for his "Inspector Morse" series of novels, which were written between 1975 and 1999 and adapted as an ITV television series, "Inspector Morse", from 1987 to 2000. His characters have spawned a sequel series, "Lewis", and a prequel series, "Endeavour".