A murder mystery party works with 6 or more guests playing different characters at a gathering or meal. A fictional character has been murdered and the aim of the game is to guess who amongst your friends did it, going on conversations and events that arise throughout the course of the evening.
In my opinion, however, the aim of the game is to have as much fun as possible playing your role and watching others around you in character.
Each guest will be given an individual booklet which includes a "character breakdown", how they should act and speak, their attitudes towards other guests, why they are there and their relationship with the deceased. There are normally four or five parts to my murder mysteries, which work well around a 3 course meal. For each section or "round" every booklet will indicate various points characters must raise or certain actions that need to be carried out.
These may include revealing secrets, evidence, alibis or reacting to other guests. The conversation normally becomes heated and revealing as the night goes on. And everyone is left with clues, evidence and plenty of suspects for the murder.
When the game is drawing to a close every player takes a guess as to who is the murderer, taking into account everything they have heard throughout the evening. Then it is time for the murderer to confess. He/she normally has the confession in the back of their booklet and explains to the group why and how they did it!!