Beneath the Planet of the Apes (1970)

Following the events of Planet of the Apes, time-displaced astronaut Taylor and the mute Nova ride horseback through the desert of the Forbidden Zone in search of a new life far away from Ape City. Without warning, fire shoots up from the ground and deep chasms open. Confused by the strange phenomenon, Taylor investigates a cliff wall and disappears through it before Nova’s eyes. The phenomenon disappears, leaving Nova alone.

Elsewhere in the Forbidden Zone, a second Earth spaceship has crash landed after being sent to search for Taylor and his crew. Brent and his Skipper are the only survivors, though the Skipper dies shortly after crashing. Brent, while noting he is in the year 3955, assumes he has travelled to another planet. After burying his Skipper, he encounters Nova and notices she is wearing Taylor’s dog tags. Hoping Taylor is still alive, he rides with her to Ape City, where he is shocked to discover the simian civilization.