Instructions
Determine how many people you want to be involved in your mystery game. You want to be able to adjust your plot based on the number of guests/suspects playing, Have an idea ahead of time of the number of people that will want to play.
Write the story. Create a story that involves approximately six to eight characters. Each suspect must have a motive. When creating your plot, consider the interests of your guests and develop a plausible reason to explain why they have been brought together. For example, if a lot of the guests are cooks, you may want to have a mystery surrounding a murdered chef.
Create actions that will move the game along. For example, 20 minutes into the party an action should occur that will reveal a physical clue that makes one of the suspects appear guilty. Stick to your schedule once you start the game so it can move along smoothly.
Create the murderer and how you intend for him or her to be caught. Toward the end of the game, your guests can try to identify the murderer based on the evidence presented.
Choose a guest to be the murderer before the game starts. Make sure your recruited murderer participates in the game by accusing the other suspects and interacting as much is possible to throw everyone's suspicions in a different direction.
Keep the guests circulating. If the guests stay in one place, they may miss important details that will help them solve the murder. Place finger foods in different areas so the guest do not stay in one area of the house.