The backstory of a script essentially concerns events which occurred before the performed murder mystery, as seen by the audience. The opening scene of the performance is the hook. This is when the murder takes place and then clues are given by the actors who will become suspects in the case. Each suspect has a motive and displays a method, for example they might hand the victim a cigar or even throw a drink in their face.
The backstory comes out as the suspects are questioned by the tables as they walk around. There is also an opportunity for public questioning where each table appoints someone to stand up and put a question to a suspect in front of the whole room. Some people revel in this opportunity to release their inner Rumpole!
A significant part of the backstory is given in the form of written clues; letters between the suspects or suspects and victims, bank statements and newspaper clippings are all examples.
Between what is seen on the night and all of the backstory evidence collected a picture will emerge and each team (table) will be able to come up with a theory covering method, motive and murderer.