You could use 'The Shadow in the Alley'. It gives a spooky and mysterious feeling. Just the thought of a shadow in an alley makes the reader wonder what's lurking there. Is it a person? A supernatural being? It sets the mood for a mystery.
One idea could be a missing heirloom. The story could start with an old family's most prized possession disappearing overnight. The main character, a young detective, could be hired to solve the mystery. He or she then discovers strange footprints around the scene and some cryptic notes left behind.
Names like 'Cipher' are great for a mystery story as it implies secrecy and mystery. 'Enigma' is another one that really shouts mystery. And 'Inspector Locke' is a name that gives the impression of a serious investigator. Locke also has a sense of something locked away or hidden, which fits well with the mystery genre.
You could have a mystery where a group of people are invited to stay in an old mansion for the weekend. During their stay, they start to hear strange noises at night. One of the guests goes missing. The remaining guests find a hidden room in the mansion that seems to hold a dark secret from the past. Maybe it was a place where illegal experiments were carried out long ago.
A short mystery story could be about a strange message found in an old book that leads to a hidden treasure. But there are clues and puzzles along the way that need to be solved.
One way is to have the first fold focus on the mystery's setup. This includes how the mystery is introduced, what questions are raised in the reader's mind at the start. The second fold can deal with the investigation process. All the clues that are found, the interviews with witnesses, and the false leads. The third fold then reveals the big reveal at the end. It shows how all the pieces of the puzzle fit together to solve the mystery. For example, in a Sherlock Holmes mystery, the first fold sets up the strange case, the second fold has Holmes' investigations, and the third fold is his explanation of the solution.
Maybe there's a powerful villain who has stolen a special artifact from both Konoha and Coolsville. Naruto teams up with Mystery Inc. to track down the villain and retrieve the artifact. Along the way, they learn about each other's cultures and ways of doing things. Shaggy and Scooby could be really amused by Naruto's shadow clones while Naruto might be intrigued by the Mystery Machine.
One idea could be to cross Martin Mystery with another supernatural - themed show like 'Scooby - Doo'. Martin and the gang could team up with Scooby and the Mystery Inc. to solve a mystery that involves both their universes. Maybe it's a mystery where the monsters from Martin's world are being controlled by a villain from Scooby's world.
One idea could be to cross Martin Mystery with another mystery - solving show like Scooby - Doo. Picture Martin and his team joining forces with the Mystery Inc. gang to solve a supernatural mystery that spans across both their universes.