Hopper, portrayed by Andrew Wilson, is an archaeology professor on a quest to uncover the mystery behind a group of missing hippies from the 1970s. His exploration leads him to a remote cave system, where he stumbles upon the vehicle that belonged to the missing individuals. After a peculiar encounter with what seems to be a stationary cowboy in a tunnel, he returns to the town and abruptly dismisses his graduate students, Jackie, played by Brianne Howey, and Taylor, represented by Reiley McClendon, declaring their research has reached its conclusion.
Driven by curiosity and concern for their mentor, Taylor and Jackie, alongside their friend Cara (Cassidy Gifford), her sister Veeves (Olivia Draguicevich), and Furby (Max Wright), venture into the cave system to search for Hopper after several days have passed without any word from him. They make their way back to the van Hopper discovered and, through the photographs left behind, learn that the missing hippies are actually Hopper's parents. Following his trail leads them to an entrance equipped with climbing ropes, prompting them to descend into the unknown, while Furby opts to remain at the base camp as a precaution.
As they navigate deeper into the cave, the group hears eerie sounds and encounters the very same invisible barrier experienced by Hopper. In a surreal display, Hopper witnesses the cowboy walk away as the world outside undergoes rapid light changes, with shadows of sunrise and sunset flashing in mere seconds. Upon exiting the cave, Hopper finds his jeep overrun with plants, a sign of time passing differently outside, and he discovers the cars belonging to Taylor and Jackie appear to have been abandoned for years. Returning to the depths of the cave to locate his students, communication fails when Furby doesn't respond, prompting Jackie to attempt a climb back out, only for her to sustain injuries when the rope frays.
In their desperation, they receive a faint call for help, which seems to be Furby's voice, leading them toward a grim discovery of his lifeless body at another cave junction. As they go through his video recordings, it becomes clear that time inside the cave moves far slower than outside; Hopper's search for his sister aligns with his parents' quest for the legendary Fountain of Youth, believed to be intertwined with the cave’s mysteries.
Realizing the severity of their situation, Taylor deduces the cave to be a surreal time distortion, causing years to pass in moments. Cara attempts to climb out for a GPS signal but is met with a desolate landscape and ominous storms, culminating in the sight of a massive object orbiting the Earth. Returning inside, she and Taylor confirm their theories as they analyze video footage, revealing that Furby had survived initially but was ultimately killed by a caveman.
In a series of harrowing events, Cara, Taylor, and the group face the threat of ancient tribes when a futuristic spaceman intervenes during a brutal clash with the cavemen. Despite their efforts, the spaceman suffers fatal injuries while trying to protect them, revealing through media clips that humanity has evolved into a space-faring civilization. As they navigate this chaos, the stakes are raised when Taylor discovers Hopper gravely injured alongside his sister and a battalion of conquistadors, all fighting over control of a waterfall deep within the cave—essential to understanding the time distortion.
In an emotional farewell, Hopper instructs Taylor to escape and save their friends while the battlefield cracks open around them. As the chaos unfolds, Cara is dramatically pulled into a portal by futuristic beings. Moments later, Furby awakens alongside Hopper and his family, having been revived by the healing waters. The group emerges into a space station, meeting up and expressing their relief and joy to share the unbelievable stories of their survival.
