cliff-hanger (n.)

also cliffhanger, "suspenseful situation," 1950, a transferred use from an earlier meaning "movie serial" (1937), from cliff + hang (v.). In some U.S. continued-next-week silent cinema serials in the "Perils of Pauline" days, the episode often ended with the heroine "hanging over a cliff from a fraying rope through which the villain was sawing with a dull knife, to be saved by Crane Wilbur or Milton Sills" [Collier's magazine, July 6, 1946].