cliffhanger

/ˈklɪfˌhæŋ·ər/ n [C]

Definition

› a story or situation, often dangerous or of great importance, where two opposite results are possible and you do not know what the result will be until the last moment: The polls are too close to call, and it looks like this election is going to be a real cliffhanger.

(Definition of cliffhanger n from the Cambridge Academic Content Dictionary © Cambridge University Press)