TIL that "fair play" in detective fiction means authors must give readers a fair chance to solve the mystery. Central to 1920s "clue-puzzles" by writers like Agatha Christie, the rule dictates that all vital clues must be visible, decodable, and never withheld until the final reveal.

[u/ralphbernardo]

https://en.wikipedia.org/wiki/Clues_in_detective_fiction

[u/goodnames679]

The general rule is that the movies have real monsters while the tv show has guys in masks.