Mystery fiction is a type of story where there is usually something that has happened that people can't figure out. It is like when you lose something and you can't find it. A mystery story tries to help you find the answer to the things you can't figure out.
In a mystery story, there is usually a detective or a person who tries to solve the mystery. This person might be a police officer, a spy, a private investigator, or just someone who is really good at solving puzzles. They try to figure out what happened by looking for clues, interviewing people, and trying out different theories.
The mystery story usually starts with something that has happened. For example, maybe a diamond has been stolen from a museum or someone has been murdered. Then the detective or the person trying to solve the mystery starts to look for clues and ask questions. They might figure out that someone had a motive for stealing the diamond or killing the person. They might figure out that someone had the opportunity to do it because they were in the right place at the right time.
As the story goes on, more and more clues are discovered. Sometimes there are false leads or red herrings, which means things that seem like clues but really aren't. But eventually, the detective or the person trying to solve the mystery figures out what happened and who did it.
Mystery fiction is a fun type of story because it challenges you to think and try to solve the puzzle. You might even be able to figure out the mystery before the detective does!