As the world waits for the return of a crew of astronauts from a deep-space mission, Thelma Joyce, Belinda Mayne appears on a television talk show to discuss caves, and the moment she speaks, a chilling psychic vision gnaws at the edges of reality. Shortly after, the spacecraft returns to Earth empty, its occupants vanished, leaving a hollow sense of dread in its wake. On a sunlit beach, a young girl discovers a strange, blue pulsating rock. When the mother comes to check on her, she discovers a nightmare—her daughter’s face is ripped apart in a way that defies explanation.
To uncover what links these eerie events, Thelma and her husband Roy, Mark Bodin along with a circle of friends, decide to explore a distant cave. They pull over at a roadside café to stock up and suit up, the hum of anticipation mixing with a growing unease. Burt, the first to notice something off, pockets a blue rock he finds near the road, tucking it carefully into his pack with a stubborn curiosity that will prove fateful. The group presses on toward the cave, their spirits a blend of bravado and fear, each member braced for whatever darkness lies beneath the earth.
Inside the cavern, they descend to the bottom and set up camp for the night. The next morning brings a terrifying turn: Jill, the friend who has taken the dive into fear with them, discovers that the pulsating stone is more than a curiosity—it's a doorway. The rock opens, and a creature breaches the surface, shredding Jill’s face in a single, horrifying moment. The sight shatters the group’s nerves, and Thelma’s Cassandra-like intuition tightens into a resolve to survive what is unfolding before them. Roy, trying to keep calm in the chaos, retrieves Jill’s body, but the danger is far from over.
The group manages to haul Jill up toward daylight, but a second predation erupts from Jill herself, a merciless monster that drags Roy by the neck and slices through his torso until his life bleeds away. Panic fractures into disarray as the survivors scramble to recover their gear and find an escape route. They divide into teams to search for a way out, but the labyrinth seems to have other plans.
As the danger closes in, Maurine, Benedetta Fantoli stumbles upon what looks like a living wall that reaches out and pulls her in, dragging her to a brutal death along with Burt, who makes a valiant attempt to save her. The tension inside the cave rises to a fever pitch. Roy suffers a sprain and is forced to rest, while Cliff, a member of the group, volunteers to locate Burt and Maurine. Thelma, trying to stay connected to the outside world, telepathically warns Cliff of a lurking threat, but the communication ends in tragedy when Cliff is killed by an unseen force.
When Thelma and the others discover Cliff again, they reveal a horrifying truth—the man they believed to be their ally is actually an alien in disguise. Thelma taps into her own extraordinary abilities and uses them to blast the imposter’s head, exposing the alien to the light of the world. With the imposter defeated, the remaining survivors—Thelma and Roy—flee deeper into the unknown, pursued by a relentless alien.
They manage a perilous escape back toward the city, stumbling upon a police car only to find it empty of all life. The roadside café and the familiar streets they once knew have become alien-toed graves of civilization; no operators answer payphones, and no people roam the town. The sense of isolation grows heavier with each step as they fight to stay ahead of the invaders who now seem to govern the world from the shadows.
Reaching a desolate urban landscape, Thelma and Roy find no one, no convenience, no hope—only emptiness. They duck into an old bowling alley they had spotted earlier, thinking they might find shelter or any signs of life, only to be confronted by another alien waiting in the back. Roy darts for cover, but the creature is quicker, and he falls to the oncoming threat in a brutal moment of violence.
The last stretch of the film follows Thelma as she races through the empty city streets, crying out for help that never comes. With every passing moment, the sense of doom tightens around her until a chilling on-screen message erupts, a warning that seals the fate of Earth: > You may be next!
