The sign of the four

Sir Arthur Ignatius Conan Doyle KStJ, DL (22 May 1859 – 7 July 1930) was a Scottish writer and physician, most noted for creating the fictional detective Sherlock Holmes and writing stories about him which are generally considered milestones in the field of crime fiction. He is also known for writing the fictional adventures of a second character he invented, Professor Challenger, and for popularising the mystery of the Mary Celeste. He was a prolific writer whose other works include fantasy and science fiction stories, plays, romances, poetry, non-fiction and historical novels.^[1][1] [1]: https://en.wikipedia.org/wiki/ArthurConanDoyle