A good idea for a short mystery story is a cursed object. For example, a beautiful antique mirror that brings bad luck to anyone who looks into it. People start having accidents or misfortunes after looking at it. The mystery could be about finding out the origin of the curse and how to break it. Another is a missing heirloom that has a lot of sentimental value. It was last seen in a particular room of an old mansion. The main character has to search through old family secrets and hidden passages to find it. Also, a mystery about a strange symbol that keeps appearing around town. No one knows what it means, and it seems to be linked to some sort of underground cult or a long - lost treasure.
One idea could be a murder in a small, seemingly idyllic town. The victim is a local shop owner. The detective discovers that the motive is related to a long - hidden family secret. Years ago, the shop owner's family had cheated another family out of a valuable piece of land, and the killer is seeking revenge for that injustice.
A murder occurs in a theater. The victim is an actor. The killer could be a jealous understudy who was constantly overshadowed by the victim. The understudy saw an opportunity when the actor was alone backstage and struck. The detective finds out by looking at the understudy's rehearsal schedule which shows they had ample opportunity to plan the murder.
Write about a strange object that washes up on the shore of a beach town. It's a small, metallic cube with strange markings. A local scientist starts to study it, but soon realizes that it seems to be emitting some sort of signal. Strange things start to happen around the town - electronics malfunction, animals act strangely. As the scientist tries to figure out what the cube is and where it came from, she uncovers a mystery that might involve an extraterrestrial origin.
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.
Effectively using good ideas for short mystery stories requires careful planning. Let's say you have the idea of a mystery surrounding a haunted house. First, research haunted houses to add authenticity. You can then introduce the main character, perhaps a skeptic who is forced to stay in the house. As the story progresses, use the setting to your advantage. The creaking stairs and cold drafts can be clues or distractions. Create a sense of urgency. The character might start experiencing strange phenomena that seem to be getting more and more dangerous. For the ending, you can either confirm the house is truly haunted or reveal a more rational explanation, like a neighbor playing pranks. But make sure the ending ties up all the loose ends and leaves the reader satisfied.
A good idea for a mystery story could be centered around a series of anonymous letters that are being sent to different people in a community. These letters contain cryptic messages that seem to be leading to some sort of impending doom. The detective or the main character has to decipher the codes in the letters and figure out who is sending them and why. Also, a mystery about a locked room where a person is found dead with no obvious way in or out is always interesting. Or perhaps a story where a young heir suddenly disappears on the night before they are set to inherit a large fortune.
You could base a mystery story on a cursed painting. The painting has a strange history. People who own it start experiencing bad luck or seeing strange apparitions. Is it a hoax, or is there something truly supernatural about it? Also, having a detective character who has his own personal demons can add depth to the story. He's trying to solve the mystery while also dealing with his own problems, like a drinking habit or a broken relationship.
One characteristic is a sense of intrigue. They often start with a strange event or situation, like a sudden disappearance or an unexplained death. For example, in many short mystery stories, the opening scene hooks you right away.