What is a mystery? It can be a secret. It is something that is not known. A mystery can be a story where the reader has a job. The reader has to solve the mystery. There are clues in the story. Usually, by the end of the book, the mystery is solved.
Sir Arthur Conan Doyle was a mystery writer. He was most famous for creating the character Sherlock Holmes. Holmes was created on January 6th. Sherlock Holmes was a famous detective who solved mysteries. He used clues. He looked at every possible answer. He had to be sure before he crossed off an answer. Whatever answer was left was the answer to the mystery.
At first, Sherlock Holmes solved mysteries by himself. A friend of Doyle's thought he needed a partner. Dr. Watson was created. He was Sherlock Holmes's partner.