The one thing I love about supplying murder mystery plays to my clients is the variety in their approaches to performing them. However, there is a basic outline to the evening that most of them follow.
The audience is sat around tables in teams. There may be a bar or a supper arranged. Some groups have even laid on a three course meal.
There'll be an opening speech from the compere, welcoming the audience and explaining how the evening will run. This is followed by 'the play' which will involve one or two murders and some revelations about the characters.
After this there may be an interval which is then followed by 'question time' when all the suspects return to the stage to be interrogated by the audience. This is a chance for the actors to prove how well they know their characters and ad lib to their heart's content. Expect the audience to come up with questions the author would never have devised in their wildest dreams. And by the way, only the murderer can lie.
Once this is finished, the teams are given some 'deduction time'. Then the suspects return to the stage and the murderer or murderers make themselves known. The teams who have guessed correctly go home with a prize.