closed circle (of suspects)
A term from mystery fiction referring to a situation where a group of people are isolated and one of them must be the culprit. Often used in discussions of detective novels, films, and games.
This mystery novel is a closed-circle story set in a mountain lodge cut off by a blizzard.
In a closed-circle setup, a crime from outside is impossible.
Variant with interpunct; less common but seen in some contexts.
Borrowed from English 'closed circle'. The term is used in Japanese mystery fiction criticism and fandom.