Codes and conventions of mystery

Definitions of the mystery genre:

'Mystery film is a sub-genre of the more general category of crime film and at times the thriller genre. It focuses on the efforts of the detective, private investigator or amateur sleuth to solve the mysterious circumstances of a crime by means of clues, investigation, and clever deduction.'

http://en.wikipedia.org/wiki/Mystery_film 


'Anything that is kept secret or remains unexplained or unknown: the mysteries of nature.

Any affair, thing, or person that presents features or qualities so obscure as to arouse curiosity or speculation: The masked guest is an absolute mystery to everyone. 

Any truth that is unknowable except by divine revelation.'

http://dictionary.reference.com/browse/mystery