Hopper, an archaeology professor, is exploring a remote cave system on the trail of missing hippies from the 1970s. After discovering what appears to be a cowboy paused in place in a tunnel, he returns to town and dismisses his graduate students, Taylor and Jackie, stating that their research is done.
Several days later, as Hopper has not returned, Taylor and Jackie go looking for him, with their friend Cara, who brings her sister, Veeves, and her friend Furby. Following Hopper's trail to the campsite by a cave, they find an entrance with climbing ropes leading inside. They decide to follow it, but Furby chooses to stay behind as backup for the base camp. They lower themselves into the cave, hearing strange noises. When Furby does not answer their radio calls, Jackie tries to climb back out, but the rope frays, and she falls, injuring herself and Taylor. Calling for help, they receive a transmission from inside the cave and follow it.
At a different junction, they discover another opening to the cave and Furby, dead with a broken neck. Watching his video recordings, they notice several days elapsed from his perspective, while only an hour had lapsed in the cave. He began researching the hippies' belongings, discovering they were Hopper's parents and that he was searching for his missing sister. His parents were following legends of the Fountain of Youth and speculated that this cave system was the root of the story. Furby found another cave opening. After several days, he went into the cave to retrieve keys for a vehicle but fell when his rope severed.
Taylor deduces the cave is inside a time distortion where events move more slowly. With few options, Cara free-climbs out of the cave to get a GPS signal. Outside, the terrain has become barren, and there is no signal. Returning to the cave, comparing video recordings, Cara has experienced about 30 minutes on the surface while she had been gone at most a few seconds from their viewpoint, confirming Taylor's theory. Reviewing Furby's footage again, they learn he survived the fall but was murdered by a caveman. Cara and Taylor deduce the time difference is much more drastic than they suspected and entire years are passing within seconds, meaning the few hours they have been in the cave is enough to span several hundred or thousand years outside.
Hearing more howling, Cara prepares to climb out again for help but is interrupted by a futuristic humanoid spaceman descending via a retractable ladder. A caveman suddenly attacks, but is subdued non-lethally. They flee just to find a whole tribe of cavemen inspecting the dead bodies of the cowboy and Hopper's parents. Discovered, Taylor fights the cavemen and is killed. The spaceman returns, protects the others from the cavemen, and then places Taylor into a healing pool of water. More cavemen attack, and the spaceman is fatally wounded, but uses his dying breaths to show them several media clips about their disappearance and indicating that humans have become space-faring.
Taylor finds Hopper injured in front of another time dilation, containing his long-missing sister and a legion of conquistadors in battle with the cavemen over control of a waterfall, the source of the time distortion, at the center of the cave system. Hopper explains the field is strongest here, making rescue of his sister impossible; he tells Taylor to go and save the others, as he is also dying. Preparing to leave the cave with the spaceman's ladder, the students are attacked by cavemen before they can get through; Cara is pulled through the portal by future beings before she can help her friends. From their perspective, she reappears through the portal, differently dressed and with rope-like mechanisms which pull her friends through.
A short time later, Furby awakens, along with Hopper and Hopper's family, all having been retrieved and resurrected with the healing waters. The others arrive, happily explaining they are in a space station and have a lot to talk about.
The film was initially conceived as found footage.[1] Shooting took place in Texas. Co-director Mark Dennis cited 1980s films, such as the Indiana Jones films and The Goonies, as an inspiration, in particular those films' focus on practical effects, characters, and plot. Setting the film in a cave came from both growing up in Texas, where caves are plentiful,[2] and from The Descent. The premise came from a four-year-long trip to the South Pole that Dennis took. When he returned to the United States several years later after having been out of touch with his friends, he was surprised by how much had changed.[3]
Based on 13 reviews, the film holds a 62% approval rating on Rotten Tomatoes with an average rating of 6.00/10.[4] On Metacritic, the film scored 46 points out of 100 based on 4 critic reviews, which indicates "mixed or average reviews".[5] Gary Goldstein of the Los Angeles Times described the film as "a handful of intriguing ideas in search of a more cohesive and dimensional narrative".[6][7] Though labeling it a good film, Roman Morales of Ain't It Cool News wrote that the film's pacing and excessive exposition keep it from being great.[8] Danielle White of the Austin Chronicle gave the film one and half stars out of five, commenting, "If anything, there’s wasted potential with the plot and story development. And, of course, some logistical points that don’t make sense. But it’s also really short. Most films that traffic in such heady subjects are, like, three hours long. An anxiety-ridden contemplation on history and mortality simply needs more time."[9]
